I hope I'm not opening a big can of worms by asking this question....

My question concerns usage license of some type.

As an amateur photographer who manages to take decent photos from time to time, I get asked to take images for whatever occasions and reasons, paid or unpaid.

Problems occasionally crops up when I hand over the prints (analog) photos or image files. (digital) Latter case is off topic here but the problem is the same in both cases. My "client" or friends would like to have my written permission so they can use the photos on web pages or get them printed somewhere.

I have no problem with their intent but I am at a loss as to the wording to use - to allow enough but not to sign my life (future work and other work) away accidentally. Basically, I want to say, such-and-such person has my permission to use the specific image(s) given by me for his/her personal use.

Just recently, I took a portrait of a friend. Our local Walmart (of all places) refused to print them because it was a "professional studio work." I had to go there personally and sign a waiver.

Would anyone be able to give me a pointer or a sample/template? Obviously it would be the best to consult an attorney but being an amateur and still in learning stage, that would be an overkill. I am not encroaching on professional's possible job opportunity either as they would never pay a pro to take photos for them for occasions I shoot. Right now, I'm just trying to save myself the aggravation without giving away everything.

Thank you.