Rule #1: Don't buy anything...YET!
Rule #2: Pay attention to Rule #1.
Rule #3: Get instruction from a qualified instructor -- who is not your spouse, parent, lover, paramour, etc. Being a good fly fisher does not mean one is a good instructor.
Rule #4: Don't fall for the old "Honey, you can have my old equipment to see if you like fly fishing." (translation: Now I can dump my old stuff and get some good equipment.)
Rule#5: Learn the basics before the trip. Otherwise, it's like entering the Indy 500 to learn to drive. Avoid the painful acquisition or distribution of unwanted ear jewelry. Take casting instruction, and make time to practice before you go.
Rule #6: Read a little, watch a little, think a lot, then do.
Rule #7: Practice yields proficiency. A good 20 minutes, three times a week, is better than a marginal 60 minutes once a week.
You don't always fish in ideal conditions. You shouldn't always practice in them either. Play with the wind, selectively knock some snow off branches or cast to bunny tracks one set at a time. (Click on print to enlarge).