I'm thinking about NBA, and am a member of the tennis and mlb.

Your plan is good, pick up packages as they start. I'd wait on tennis until January, since the season is nearly over.

You'll wanna open at least a few online accounts. Just offshore (caribbean) for the moment since you'll be betting NBA. A must is pinnaclesports.com. Great lines/odds, very fast transferrals and good customer service.

You'll want to look around. A lot of books offer low vig (low house edge) on certain days of the week. -110 is the norm (same as $1.91 in decimal), but low vig is usually
-105 (1.95) and sometimes even -102 (1.98).

Having at least a few accounts allows you to shop, and generally is worth around 2% on turnover. Bonuses are worthwhile as well.

You'll want to research the book before you open an account. Use sportsbookreview.com to get a general idea (they are sometimes biased though). Also check out forums, especially sharpsportsbetting.com. There are quite a few pro's there and they'll know which books are good and which are not.