Pick your time. Usually bike shops have their sales in the fall when you can get a previous year model at a good discount.

Avoid carbon fiber frames and pro level gruppos. Go for an alumninum frame and a Deore gruppo as it's gonna save you a load of cash and give you a good bike to get started.

Save some cash to buy a new saddle. Usually the saddles that come with lower cost bikes are incredibly uncomfortable. Money spent on a good saddle is money well spent.

Most importantly, enjoy your bike as much as you can!