Type of terrain
The first thing to think about is the type of surface you'll be playing on.
If you plan to play on natural grass or long artificial grass, you'll want to opt for a firm ground (FG) model with moulded studs for good traction or a multi-ground (MG) model with a pivot point for easier direction changes and excellent traction.
For playing on short astroturf or sand-dressed pitches, choose a hard ground (HG) boot style. Short rubber studs will give you the traction you need.
To play on soft natural grass, you should choose a soft ground (SG) model with screw-in aluminium studs.