Play Diplomacy Online

(I've gone back in the Forum over five years, and haven't seen anything that looks like this. So I thought I'd ask....)

Well, things didn't go well for you at all, did they.

You bungled your first builds (wrong units, wrong places), didn't see alliances coming, misread other players intentions towards you, and now you're down to three units - at most.

But you have been having a great time playing, and you want to keep going as long as you can. Even though there's no chance at all you can have an affect on the final outcome, and can get wiped out in a few turns if all your neighbors gang up on you.

What's your strategy for sticking around as long as possible, with just simply mutually supporting all your units to Hold in place?

I find your core premise--that a 1-3 unit power cannot have any significant effect or an outcome and is powerless to take a share of a draw or even make a comeback--to be fundamentally flawed.

However, since your question applies to all down-on-their-luck powers and not just the ones that have given up hope, I would suggest the following:
1) Communicate constantly and with everyone. Even people who don't return your messages. Be funny. He helpful. Make yourself someone that others don't want to see gone. Probe for as many possibilities for help, peace, and alliance as you can find.
2) Look for a way to make yourself valuable to someone. This includes finding a way to make yourself a threat to someone.
3) Look for a key position that can be defended.
4) Hang on for dear life to as many home centers as you can--they're usually the only place you can build if you start to make a comeback

While I do believe in the chip and a chair for the most part, occasionally I'll go MADD, or it's subtle cousin KingMaker

become one of you neighbor's front line so you are positioned in a way that if they take your centers from you their front line (you) collapses.

and make sure they know it.