This page contains spoilers for finishing missions.
Entourage
Full armor/health would be nice, but a health pack is easily available if you need it. Bring plenty of ammo and some grenades.
When the action finally starts, you are in an alley. The guy you are protecting stays hidden and is not a factor.
Your most immediate threat is in the alley across the street, so take them out first. Look for red dots with arrows on them across the street from you and take them out next. Then take your time and clean out the rest. Reinforcements for them usually come, but should be no problem.
You may get a red dot hiding from you. One place is in a nook around the corner to the right. Another place is in an alley to the right of the first alley BGs were shooting from.
Stay against the building on your right when you go after these guys, then run across the street at the corner if you need to so that the BGs on the roof above your original position don't get you. When all the street-level BGs are taken care of, get those last couple of guys on the roof.
You may have to go back down the alley to get the guy you are protecting. There is a health pack there if you need it. Get into the front car by the alley and wait for four cars of BGs to arrive. If they don't come right soon, try pulling straight out of the street and when you see their red dots on your HUD, back straight to where you started.
If they stop at the end of the street and fire at you, you can stay in the car and shoot back, but after they all arrive, you'll want to crash through them, turn right, and gun it. There is a randomness to the game, but this has been tried several times and always worked.
If you try to run for it immediately instead of using the above approach, they will be on your tail and it will be more difficult to shake them.
Dining Out
You will need a vehicle that you don't want back, full armor/health, and a full stack of RPGs.
This is a great gun battle with some unusual techniques involved. When you first get to the restaurant, drive a large car around back and park it tight against the front of the car that is already back there. More about that later. You may notice a ladder going up the back of the building, but don't waste time with it; the door at the top won't open to the inside.
Now go back around front and enter the restaurant. After the cut scene, go around to the left of the guy and shoot him with a shotgun, but not until the cut scene is done and the manager's blue dot shows up your HUD.
The reason for going around to the left is that another Bad Guy will appear in the room to your right and start shooting you as so as you shoot the first BG if you do NOT move. Now you can move around the wall on your left, press RB to get in the Cover mode, lock on the BG in the next room and shoot him.
Get out of the cover mode and get into a position to lob a grenade into main dining room beyond the room you just shot the 2nd BG in. After you throw it, move out of range to the left and bring up your RPG. Go to the doorway of the main dining room. There should not be any BGs on the ground floor. If anyone is shooting at you, fire an RPG at them. Be sure to aim over their heads because you don't want the blast to hit the railing and blow back on you.
Run over to the post on your left and fire another RPG to the right, even if you can't see anyone. Sprint across the room behind the stairs and fire a couple of more RPGs into areas you have not hit yet. If you cover the entire upstairs area, that should take out most of the BGs.
Switch to an automatic weapon, run up the stairs, turn around, and start shooting BGs. You should have started this phase with full armor or close to it, so don't worry about take a few hits, but if it gets to be more than that, crouch and/or take cover. If someone is blind firing from behind a post, press in R (Right joystick) to zoom-aim on them with your automatic weapon and shoot whatever part of them sticks out.
After you have apparently finished them all off, you can run around the room picking up weapons if you want. There's no hurry, but there is probably one more guy left hiding that you will have to take out. After you circle the room, go into the office.
Normally, there is nobody in there but the manager and he is unarmed. Pull LT to target him and he will tell you where the boss is. A nice, new body armor is on his desk, but unless you are low on health and body armor, don't pick it up yet because when you go out the door, you are going to have to deal with another four or so BGs.
Fortunately, there is still no rush, but there is also no reason to play it too safe because in addition to the body armor, there is a health package in the kitchen. Again you may have to zoom-shoot parts of anyone who is blind firing.
When you finish these guys and start for the kitchen doors, a BG may come out. He is easy pickings. If he doesn't come out, stop a ways back and shoot the door to make it swing open and then shoot the guy.
Another BG will be to the right of the door frame. Throw a hot grenade into the kitchen to get him, and while waiting for it to blow, change to an automatic weapon. After the blast, run through the kitchen, out the back door to a fire escape.
The boss' getaway car is in the parking lot below, just to the right, and still blocked in by the car you put there, assuming that you got outside fast enough after the kitchen doors opened (which is when he takes off).
The boss will be the guy with the red marker above him and should be an easy hit.
If you are not in time and he drives off, go down and get in the car you parked there, not the motorcycle that you would have had to take otherwise, and pursue him. This is an odd chase in that the BG's car goes really slow, and you could go out for lunch and he would still be waiting for you. Keep shooting at his car (which has a guy shooting back at you) and eventually it will either burst into flames or you will kill the boss.
Liquidize The Assets
You will need full armor/health, ammo, RPGs, and grenades. Something that will make the mission a lot easier is an armored car. If you looked ahead in the past, hijacked one and kept it in one of your safehouse parking spaces for just such a mission, then now is the time to go get it. If you don't already have one, you can usually find some on the road in front of Brucie's.
After talking to Jon G., drive your tank over to the destination. When you get there, you will see a tall wire fence with a concrete driveway sloping up from it to where you can see BGs milling around. Drive through the gates and try to smash as many BGs as you can with it. Of course, the BGs will be firing at you like crazy, which is why an armored car is nice to have. Even so, you cannot spend too much time doing this because the real risk is that one of the guys will open the door and pull you out.
So eventually you will have to park it and get out. The place to park it is blocking the top of the concrete ramp with the driver's door away from the action. Then you can get out and have pretty good protection with it from the snipers on the roof as well as the guys left on the the ground. Your immediate concern should be with any guys on your left.
After taking them out, concentrate on the guys on the roofs. From behind the armored car they should not be too big a problem, and then anyone on the ground level will be even easier.
The red dots left after all the carnage appear to be for the five vans you need to destroy, but there are not necessarily any BGs left. You could use grenades and/or RPGs to destroy the vans, but if you don't want to waste the money, just keep firing into the radiators until the vans catch fire and blow.
The reason for the armored car, aside from squashing BGs and providing cover, is to block the driveway, which is the only exit, in case someone tries to get a van out. If one gets away, you fail the mission.
If you can't get an armored car, here is a more subtle approach:
When you get to the point where the cut scene kicks in to start the action, take a car around the left corner (you are actually turning right at that corner) to get to the left side of the building which is protected by a wall with a fence on top. Drive down by the phone booths where the wall is short and smash the fence with the car. Get out of the car and walk into the compound.
After you walk around the corner next to the fence, you may see a BG pushing a cartload of boxes baack and forth. Start the action by shooting him. Then work your way forward from there, taking cover, shooting blind, and watching for the guys on the roofs and the bad guys charging you. A couple of well-cooked grenades into the courtyard seem to help.
You can take as long as you want, but this is a very difficult battle in this subtle approach. After you get most or all of the ground troops, you can go to the back of the structure you are standing next to and pull yourself up on top of it, advance to the corner of the building and go into the Cover mode.
This makes it easier to aim at and shoot the roof guys.
The real problem with this approach is that if one of the vans which you cannot see down the driveway to the back right decides to make a break for it, you may not be able to stop them as they blast down the ramp. This is where the armored car blocking the ramp would come in handy.
If you suspect they are going to come, you can target where they will come out of the back right driveway and hit them immediately with an RPG, but if you miss or are too slow, you can't RPG them once they get too close to you and they will most likely get away.
Bottom line is that it is probably worth the effort to get the armored car.