I like everyone else will suggest that before buying a lot of gear, try to at least do some small trips. Figure out what you really need and get acquainted with what you actually use and what you end up just hauling around.
I think the greatest recommendation I can make, especially if you're planning to go light, is to do it from the beginning. Spend a lot of time researching and figuring out what is really out there. This may warrant asking more questions here in the forums to really find out what cottage co.'s and such are out there and the products they provide. Even to this day I find out about small ops that I never heard of prior. And some of them are some excellent niche products that nobody else makes.
Now that I think of it, I think the greatest recommendation I can actually make is to study the equipment you're thinking about and imagine yourself using it. This may be easier to do after a few small trips with whatever you have right now. This has been a great help especially when choosing a shelter, clothing needs, etc.. You've got to get into the mode of questioning yourself a lot.
- Do I really need this?
- How often will I use it?
- Is there a lighter alternative?
- Do I have something around the house that both free and lighter?
- Can I use this item in more than one way?
- Is this more space than I really need?
- Is this overkill?
- When setup in camp, can this item pull double duty after it has been emptied?
- What will it be like in this tent long term if caught in nasty weather?
- Can I cook safely and comfortably in this shelter?
...these are just random things off the top of my head...your questions to yourself may differ.
A lot of backpacking light is finding your comfort with less, and not necessarily just finding lighter equipment. i.e. - I was really surprised that I wasn't at all uncomfortable the first time I slept on a closed cell foam pad rather than my Exped SynMat UL 7. Each has it's time and place...but the bulk of the time the CCF pad is more than adequate and nearly 10oz lighter. You'd also be surprised at how many backpacking items that are great & cheap can be found at the grocery store, around the house, in the recycling, at the dollar store, etc..
Gotta think outside the box. Weigh everything. Make a list (or spreadsheet), look at it daily. Play around with your needs and numbers.