What sort of riding are you planning to do? Sportive, Racing, Tri-athlons? Depending on your answer, it will dictate what sort of geometry you should go for. If you want to ride for distances with comfort, you're better off with a bike with a long front headtube, which makes the bars sit quite high relative to the saddle (sportive position). If racing or tri-athlon is your cup of tea, then you'll need something with a shorter front head tube and tighter geometry which sits you further down on the bars to reduce air resistance.
How fit are you? This will dictate whether you need a triple, compact or standard chainring on your bike. A triple (three cogs on the front) gives you the maximum range of gears and willl certainly be the best choice for the beginner. A compact chainset has two rings on the front with what's generally a 50/34 combination (big ring has 50 teeth, small 34), this is better if you are reasonably fit, it has a slightly narrower range of gears than the triple. A standard chainring is what most experienced riders, racers and tri-athletes us. It is a set of bigger rings which allow you to go faster by creating harder gearing ratios.
Phils Road Biking Blog