No easy answer.
One set of neighbors throw great Thanksgiving/Christmas parties, so we'll help them out whenever they want knowing that we'll have lifetime invitations. It's usually minor electrical problems like a broken Christmas ornament or an appliance repair.
Another woman is raising three kids on her own. (I've met the ex-husband. We are not impressed.) I've shown her and the kids how to fix the easier stuff (unplugging & resetting the disposal) and I charge $25/hour for the rest. She also provides yummy baked goods so that $25/hour is highly negotiable. Better yet, when I was considering ACL reconstruction she gave me the inside scoop on a new hotshot orthopedic surgeon (she's affiliated with a local health insurer). Unfortunately her house has gone through all the easy projects and she's facing repainting, recarpeting, and attic reflective foil insulation. I think she values our advice but I'm not sure that we want to tackle something that big.
We take care of a shipmate's house/tenant, and she's extremely generous. It's almost to the point of embarrassment but we love the exotic (to us) Mainland foods she sends and we manage to cash her checks. We think she sleeps better knowing that she's paying us what we're worth and still coming out ahead of a professional management company. We almost never hear from her tenants so it's no problem.
Most of the other neighbors have asked for an hour or two of help and no one has tried to take advantage of me. We reciprocate pretty fairly/quickly and they're always very generous with holiday food.
I've turned down a couple repairs that I knew immediately were beyond my interest or my (realistic) skill level-- leaky water pipes inside the wall, mold, A/C repairs, roof replacements. After all these years on discussion boards I'm pretty much immune to appeals ("Sorry, but I can refer you to a good contractor") and baiting ("You say you know I can handle this?!? Well, I could probably figure it out on the third try after two weeks, but this is a job for a pro.") I think if I got one more phone call than I was happy to help with, I'd start responding more slowly and finding schedule conflicts.
Hasn't been a big problem yet. Most Hawaii residents are very conscientious about omiyage & obligations, and the jobs I've tackled have either been interesting/fun ("Always wanted to work on one o' them!") or good karma.
Now if you're referring to the phone calls I used to get from my father-in-law, that's a whole 'nother can of issues. Most of them had to be chalked up to my good karma and his bad...