As a relative newbie myself, I'd say read the Treasure net forums religiously. I was lurking here for almost a year before I finally bought a detector. I learned a lot from these posts and am still learning. In addition, it gets you excited about hunting. There are even sometimes now when I want to go but just don't feel like getting off my butt and then I read a few threads, get excited again and I'm out there. I think it helps to be a treasure hunter to begin with whether it be hunting garage sales, thrift stores or always scanning the ground for change and stuff. If so, you know that you don't always find great things everytime.
If you're not sure you'll stick with it, buy a used detector at a garage sale or thrift shop. A good digging tool is a must and as I learned here, the Lesche digging tools are great. Got one on eBay pretty cheap and it really improved my hunting experience vs. the old garden trowel I was using. Also don't think you have to have a high dollar detector to find things and have fun--that kind of thinking held me off buying one for awhile. In fact now, I've been tempted to upgrade but considering the kind of sites I have to hunt regularly and the luck I'm having with what I have, I haven't seen a real need to yet.
Hunt every chance you get including places you already visited. You'd be surprised how you keep finding things you missed before. Plus be realistic, the stuff found here is great but if you're hunting schools from the 1970's on, you're not going to find Roman stuff, turn of the century relics or civil war stuff. However you will find modern change, pull tabs, pencil erasers and if you're lucky, some silver and gold jewelry--the chase is better than the catch (well, most of the time)
As stated above, patience and persistence. I think flexibility helps too, sometimes I'm out hunting and get really bored or just plain tired of digging everything and getting pulltabs & trash so to keep it from becoming a chore, I turn up the detector and just hunt for dimes & bigger. If I go to a school or park, I like to hit the playgrounds first and find a bunch of change to get me psyched up before I hit the big fields--many times I find more in the fields than I do in the wood chips
The excitement for me is in getting a signal, not knowing for certain what it will be, and then digging and searching till you find the target. If you enjoy that feeling, than anything you find is a bonus.