sounds like there's a lot of good advice here, obviously we are at diff levels and im sure stuff worked better for some than others. my advice...
lessons: i started learning with a bunch of friends (self taught). it is ALOT better if you have a good patient friend that will stay and teach u, way better than trial and error. not all ppl who board well can teach. i taught my share of friends and i admit i am one bad impatient teacher. it's also tough for me to analyze noobs boarding. so if u dunno a good patient boarder willing to, then take a beginner lesson. u'll make leaps and bounds in progress over someone self teaching. u'll save money than wasting more lift tix on trial and error. u'll enjoy it better overall too because i always see self teaching ppl get really pissed and thus less likely to like boarding (i have friends who decided to retire cuz they couldnt get the carve by themselves). another thing about friends teaching, my noob friends used to tell me they didnt like us waiting for them and giving them tips because they feel too pressured to perform and theyd mess up. but if u have a paid instructor, who cares if u are making them wait for u...u'll be more relaxed. i wish i had someone teaching me when i started.
rentals: the boot is the most important to buy first. i once forgot to bring my boots and had to rent. the rental boot was all wet inside...eeeeeew. i will never forget my boots again. but if u have to rent, i suggest renting off mountain if possible (like sport chalet or dicks). their stuff should be in better condition and maybe cheaper. plus u dont have to wait in the long rental line on the mountain.
set ups: not much advice over here, just that in the end/off season there are a lot of stuff 50-70% off if you are lucky. otherwise get something used (or even new) on craigslist, nothing wrong with that. have fun!
I agree it's better to get a lesson. Most "friends" aren't snowboard instructors with experience with feedback and even some of the really good shredders don't know what they are uncounciously doing, never mind how to teach a beginner. I've had friends give noobs wrong advice. And even though I tell them that, the next time, they still give wrong advice! And they even try to teach them how to carve in the beginning, which is really an advanced technique later on. And I think one even confused carving with skidding.
I've experienced way too many times seeing someone like all day in the beginner slope "with a friend teacher" to say WTF is going on and go there to check em out...to find out the "teacher" is giving dead wrong advice. I told them that afterward and they still don't believe me even though the newbie keeps falling. They just blame it on the newbie and keep yelling at them. So I walk the newb through the "real" way and they are actually standing up and turning, etc. now. And I come back later and they are falling over and over again because the "teacher friend" is still giving the wrong advice and yelling at them. rofl!
The best advice (sarcastic) I've ever seen was "look in that direction and your board will go there". My Ash!
There's more to boarding than boarding. There's falling, one footing, saftey on lifts, drills, etc.
Be that said, if you are going to learn on your own, I've found books to be much better than "the internet". The internet has loads of videos and short snippets of descriptions, but so far, I have yet found any "free instructions" to rival the quality of something you pay for. And a good book is structured to teach you step by step. After my first day "gung-ho" and in pain afterward, I read 6 books a really long time ago to figure out what it's all about. By the end of my next day, I was doing double blacks. Not Olympic style, but maybe falling only 10% of the way at the end of the day.