Board length: Some rental shops use the rule of thumb that a board should touch between the beginner’s chin and nose. Every board feels different when you ride it. You might like a 155 of one model and a 165 of another. Like everything else, there are no hard and fast rules. Rent to begin with and try to demo your equipment before you buy.
Board width: Board width, usually measured as waist width, plays an important role in how the board works for a particular rider. Ideally the boot toe and heel are even with the board’s edges. A little toe overhang is OK but too much and the toe (or heel) will dig into the snow when turning, greatly affecting control. If the toe and heel are too far in from the edge then getting the board onto it’s edge becomes much more difficult, requiring excessive force from the rider. There are 2 factors which will dictate what board width is optimal for you: stance angles and the sole length of your snowboard boots. If you ride with your feet straight across (0 degrees) then the board width at the binding locations should be close to the boot’s sole length. If you ride with your feet at 60 degrees then the board should be significantly narrower. The stock newbie advice: suitable for most new riders who don’t yet know whether they want to specialize in some particular area, and who don’t have knowledgeable friends at hand to help them.
Brands: Since you (presumably) don’t know anything about the manufacturers, stick to the large, reputable ones: Burton, Sims, Nitro, Morrow… They’ve been making quality product for ever, so you won’t get screwed.
Style: Buy a freeriding board (e.g. Burton A-Deck), soft boots, and soft bindings.
Setup: set your stance to 20″ wide, 1″ back from center, 30 degrees on the front, 15 degrees on the back. Learn to ride, then play with the stance to see what works for you.
New or Used: You can save a bundle with a used board. Buy one that isn’t too old (it has inserts in it instead of drilled bindings), isn’t too beat up (the base and edges look ok), and hasn’t been pounded to death (it still has camber). Learning to ride: take a lesson. Really. I don’t care how good your friend is, or what kind of wicked shit they can pull. They’re not trained in giving lessons. Save yourself some bruises, invest $20, and have a MUCH better time on your first day.
Disclaimer: Yeah, it’s a boring old-school setup. Guess why? It works. It’s not optimal for jibbing, or racing, or whatever, but it works great for learning. If I didn’t mention your fav’ brand, this is not intended to be a complete list, just a simple and reliable list. If you buy a Burton, Sims, or Nitro, it may or may not be the absolute best board possible (give or take taste) but it will NOT suck, and it will hold it’s resale value so you can sell it and buy something specialized later.