It's been mentioned in other posts, but I'd like to put it at the top of the list:
Good shoes, waterproof, that fit well. Don't buy cheap junk, go ahead and buy decent shoes from a known maker (Danner, Rocky, Red Wing, etc) and be sure they are broken in before you step into the woods. Go to a real shoe store and have your foot measured by someone who knows how to do it - believe it or not, your foot changes as you age.
If your feet hurt or are cold, you'll be miserable.
I have two sets of woods shoes - a "chukka" style hiking boot I got from LL Bean, believe it or not, for only $80 on sale. Waterpoof, comfortable, good for day hikes and moderate terrain.
For bad weather and worse terrain, I have a set of the Danner boots they make for the USMC - 8'' tops, waterpoof, lugged sole.
Best of luck on your hunt,