Here it is, how I'm currently ranked #5 in the world for XBOX SOD Lifeline. This guide will show you how to dominate Lifeline from siege 1 all the way to siege 1000. First off, let me explain a few keys to the strategy:
1. Infinite Influence
This bug was in the original game and Breakdown, so it's no surprise that we see it again in Lifeline. What you need to do is strip your characters of melee weapons (I leave the guns on in case a siege happens and my guys are left helpless). Next, go out into the world with a well equipped character and just kill zombies. When you go to the journal tab and look at each of your members, you will see that the ones marked "Away From Home" have grabbed weapons for themselves. Head back with your vehicle so you don't leave it on the highway, and then switch to those characters. Sell their weapons back to the locker for free influence. Repeat for infinite influence.
It's important to place your outposts around each of the six major off ramps for the highway. All the other locations you will have to drive to when killing hordes. Do NOT allow hordes to just infest locations. For one, you'll get half the influence clearing an infestation compared to killing horde (5 versus 10). Second, you'll have more ammo costs per siege to deal with the zombie threat from infestations.
3. Danger Zones
These are great for skill ups but terrible for points. As far as I can tell, regular zombies give 0 points when they spawn in a danger zone while the specials continue to give points regardless. Here is the ultimate shooting spot where you can fire as loud as you want at 5 constantly respawning targets:
Head to the second floor of this building and break the window where the ladder is on the east side. Now, zoom out into the alley (do this during the day) and fire away with no suppressors. All zombies attracted to the noise will run underneath you so you'll easily be able to escape back to your car when you're done. You'll get tons of headstreaks and quickly have a level 7 shooter.
Here are the locations for my outposts. You want to focus on getting food and materials if possible, but honestly it does not matter due to the infinite influence bug and being able to call in supplies.
During a siege, being able to pick off ferals with single head shots is a great influence saver. So if you want you can have someone with focused aim for that reason. Otherwise, go with these specializations:
Reflex - Endurance, spin kick, no melee weapon
Powerhouse - edged, low slice (use on armored zeds)
Other - Blunt, spin or uppercut (I prefer spin so I have an option against many zeds at once)
Low sweep and low slice are strong but they don't give you kill points unless you execute.
You must have a latrine, workbench (with ammo production) and infirmary (with field surgery).
7. Grenade Launchers
Find every damn grenade launcher in the game, starting with whatever is in the police station and then move on to all the little delivery trucks scattered throughout the game. I'll let you do the finding as I honestly don't have them memorized (I picked the map clean back when I was around 20,000 points and I have a lot more now!). Use the survey locations to find most of the trucks, then check the highway ramps.
Why do you need grenade launchers? When all of your allies have them at your base, you can literally sit back and only kill the big bastards during sieges (your allies cannot kill big bastards with their grenade launchers, only you).
Keep your team small and limit it to the number of grenade launchers you have.
8. End Game
Once you've completed all the side missions and disarmed the nuke, in the words of Cartman, "Now we can finally play the game." It's time for the end game, which is not nearly as exciting as you'd think.
Besides calling in supply drops, cleaning the latrine, and having your squad look for materials, the only things you have to do in between sieges is kill hordes and wander the highway looking for zombies to slaughter. Remember that car kills only count when you destroy a horde, feral, or screamer. It counts on a boomer but please don't do that!
During a siege you can sit back and wait until your ammunition is required (thanks to all the grenade rounds flying. When big bastards arrive, use a gun that can kill them for less than 6 influence or your grenade launcher (most likely the grenade launcher will win that influence battle). At maximum siege difficulty, you will have two big bastards to kill, one from east and one from north. Remember, your allies can't kill the big bastards with their grenade launchers.
Don't get mines, firecrackers, or propane tanks, they are a waste of supplies. Do shoot the giant propane tank on the northeast corner of the base and across the street. That's a great way to get a bunch of kills when the north side spawns as well as take care of a wandering horde that gets too close during the siege.
9. How Do Sieges Give You Points
Sieges give you a bonus modifier of +.10 to your score. So if you kill 100 zombies and defeat 20 sieges, you will have 200 points. My math is not perfect but that is the general idea. With this in mind, you should work to get as many zombie kills by gun and melee as you can in between sieges to maximize your points. Killing specials and hordes give you a one time bonus, which is based on the modifier and a base amount. You do not get the modifier bonus after a siege applied to anything except regular zombie kills. At this point I'm getting like 1,500 base points per siege but people at the top of the leader board with 400,000 points are getting like 5,000-10,000. This is all because their siege modifier keeps increasing (no idea if it caps) and their base zombie kill count is going up as well.