To summarise -always get an assisted launch and land if there is an appropriate person to lend a hand, especially if the spot is crowded or there are obstacles-
beginners should definitely learn how to self launch and land this is an important basic kite skill, practice this on a wide open beach on a light wind day- check out the vids by cbulota they are the best.
Intermediates and advanced kiters- take it easy on the learners remember you were there once, be open and forthcoming with advice- try to correct bad practices but don't be a dick about it.
if you see some dodgy stuff going on be sure to try get them to stop and show them the error in their ways- managing good practices at your local is everyone's responsibility
Remember that your never too good to lend a hand and your never so good you'll never need somone elses help