Why? You can tell by the type of client whether they would be willing to pay a professional rate, or whether they are looking for something on the cheap. This in turn will give you an inclination whether to even look at the brief.
Back OT, I'd agree with the above it you're still at the learning stage.
Learning design theory as well as the practical skills such as software but one thing I'd suggest is not to forget about paper and pencil.
This is where it all starts.