A few tip for new lifleine players:
1)watch your rep/influence, airdrops are expensive and after you have scavenged for a few hours you pretty much screwed if you use it all up,the best air drops cost around 200 influence which can bankrupt you fast so resist the urge.
2) set up out posts in the buildings across the street from your base, you might think you can handle the base attacks like a boss but you'll be glad you have extra traps due to the outposts when you get hhit with waves of like 4 ferals and 3 juggernauts on top of tihe 50 zombies that are thrashing your gates, also remember to go to the house tab in your notebook to reset all the tanks/mines around your base after each assault.
3)kill zeds that are swarming high priority civilians fast, it may seem like nothing but in the time it takes you to get in a truck and start it 4 zeds can kill one civilian, I've lost like 3 people this way,mostly since I figured I had more time to save them and ended up failing,either way make sure you kill zombies near any of your mission NPC's.
A few general tips, if your near a building and are about to get into a fight, run inside, the bonus here is you can fight without loosing much stamina since indoor actions don't drain it much,actions like rolling,executions and ruck sack moves will still deplete it.
I have a rather high stamina move that allows me to hit,finish and repeat Pretty fast( jump kick--roll--execution) kinda high stamina but kills fast,works with pretty much all zed except juggernauts & bloaters.
I guess the best tip/advice for lifeline is, when in doubt,run away, no joke zeds in this city are brutal and will kill your highest trained PC in a min so don't underestimate them.