I've been asked by a few people for tips on how best to look after hair. I'm not a professional, and some of my views, opinions, and advice may contradict the things others have told you. I will simply talk about what worked for me.
Like I said I'm not expert, but I've never had any major problems with my hair, no serious breakage etc. I've never fixed a weave and I can count the number of times I've had braids. Generally, before I cut my hair, it was either in a pony-tail/bun, or it was down, free to blow in the wind (this was always more likely in the summer when the weather is good).
The whole point of a re-touch is to straighten any curly/kinky re-growth therefore waiting 6 months to do it is in my opinion pointless. Huge gaps between treatments are just as detrimental to the condition of your hair as relaxing every other week would be...
A re-touch every 6-8 weeks is ideal. Do not wash your for about 10 days before you do relax it. GO TO A SALON. I cannot stress this enough. Doing it at home is never the same. Stop being stingey and make that trip to the salon. Also make sure the people doing your hair know what they are doing.
Make sure they base your scalp properly. Don't leave the relaxer in for an hour. It is not necessary. If your hair isn't done after 20-25mins maybe you should try another relaxer or a different strength. Burnt scalps look horrible, feel horrible, and do NOT promote healthy hair growth.
Obviously they should use a neutralising shampoo. Three washes should do the trick, and then a deep condition afterwards is great.
You can blow dry or set your hair afterwards (apparently setting causes less heat damage).