I have a very much better memory for tunes than words, possibly because of early involvement in music. (can't always remember tune titles mind you. When I've HAD to learn words, e.g. for a stage production, then it was the tape in the car stereo: I used to record myself reading scripts but leaving out my own lines which I then had to fill in. For musical productions I would have my own part (alto) with NO words for tune learning, and the full works (with words) for singing words plus my part against the melody. Unfortunately usually as soon as the show was finished, the slate would be rapidly wiped clean to allow my ageing brain to store whatever else came its way!
For folk songs, I try and learn by singing along with a CD in the car: repeated reading of words just doesn't work for me: then it's "use it or lose it", i.e. keep singing it till it's well bedded in, or it just gets deleted off the hard drive. However there are some songs that are very seasonal, so I would perhaps put words in front of me and just try to get away with looking at them now and then, rather than having my nose buried in them. (Seems a lot of professionals now have the big music stand and do just that these days, especially those of us whose hard drives are getting overloaded or tired.
As fr my own songs, yes, have the words somewhere visible as unless your friends are really big fans, no-one can help you out if you forget!