Pardon my bad English grammar/spelling in advance.
In the first place if you're dropping down from 350 i would get a doctor involved before working out because not every part of your body might hold up against the work out. They can set you up with sound advice on a routine.
I never lost that kind of weight but i lost about 25 pounds this year (i'm only 5'8) just making little changes. Here are some things i do:
1. Keep a log. This sounds a little childish maybe but it helps you stay motivated and keep track of what does and doesn't work for you. I very simply write down what work outs i did that day. I got a calender up, i can tell with one look if i am doing what i'm supposed to do that day, week, month.
2. Bought an eliptical machine, used, fuck new, and do at least 40 mins a day as a rule. Might want to build up if that is too much atm. What helped was having a few series to watch. I'd just put on an episode, and get to peddling.
3. Core strenght excscxercsisxze..err training (no idea how to spell that word), look up good ones online or ask the doc about it. Doesn't drop body fat but it makes your body better able to carry its own weight. Also seeing your waist get smaller helps stay motivated.
4.1 Probably most importantly, food. I completely stopped drinking soft drinks except for light ( i drink this store brand cola light with less than 1 kc per glass) Also use sweetener for coffee and tea. Aspartham is not healthy but hey nothing is perfect. This must have cut about 750 kcals a day at one fell swoop because i was drinking damn near half a gallon of coke a day plus about 8/10 cubes of sugar a day in tea and coffee.
You'll get used to the taste in 2 weeks max and you won't even miss the "real" sugars in your drinks, i say that sincerely, not just to be optimistic.
4.2 Try not to eat after about 21:00. You can just drink tea/water/diet soda.
4.3 The obvious thing, limit the absolute junk as much as possible. Like chips, chocolate, fast food etc. Every now and then is fine but have a little and leave it at that. I really believe we are mostly drawn to those t hings because it is conditioned sense of indulgence and not because we enjoy them that much. They're not that good and as a trade off against your health they stack up even worse.