I used to try to help people out and frequently got rode hard and put up wet for my troubles. Since I don't like taking abuse from people who are not good hearted in return, I have pretty much quit. Now, I use contracts every single time, nothing is on a handshake anymore. In my contracts I spell out exactly what can be expected of me and what I expect in return. If it isn't in the contract, I didn't say I'd do it and don't ask.
Now, unless asked directly about something I don't offer an opinion, I don't offer to do a chore someone else is having trouble with and I especially don't do something that will cost me money and not get money in return. I get liability releases signed and I file them in a folder with a person's name on it, and I keep them for years.
I used to be trusting and got called a fool one time too many, now, you want trust, kindness? Earn it.