Also, be honest with yourself about what you want the suit for. For many, this is their first suit, mainly for work and interviews. In that case, two buttons, notch lapel, two vents, normal flap pockets (and no ticket pocket), etc. If you want a fashion suit (ie something you wear to social events or to an office that isn't super conservative), that's when slanted pockets, ticket pockets, peak lapels, colored buttonholes, etc become nice additions.
Yeah, agreed. Keep it simple first and learn the basics. Nothing worse than many of the guys who order their first suit online and go completely overboard with customisations that makes them look like a parrot (in an often ill-fitting suit).