First off, you need to get yourself some guns.. this is a given - remember, at 18 you can buy a shotgun or high powered rifle, if you stick to the flea markets and gun shows you can often buy with no waiting period.. you need many guns, the more powerfull the better.. you may be asking "But PhreeX, why do I need guns?" Well, if it doesnt make sense now it will later.. so have guns, lots of guns...
Also, get a welder and cutting torch, other tools are also a plus... begin to collect various metal objects, attach them together into things that make sense at the moment...
You can always clean and do other household chores - we would often come up with cleaver solutions to common problems, for instance, the house needed to be repainted but it was July and HOT .. well, there was a truely simple solution - paint at night under floodlights! Pure genius indeed!
For real though, if you have to ask then perhaps you should sober up...