I've been keyboarding since 98' so typing has never been a problem for me, but if you want some advice, just bind the !buy menu.
Things you should only really buy is:
AK for excellent spray with good power and accuracy
AWP for fast and easy kills
Lasers for accuracy obviously
Fireworks for easy common kills and to get them off of you while you're trying to aim
Pills for when you are in the red or orange, and to share with fellow team members so you don't have to heal them.
First aids to heal yourself only, don't give team mates points, you won't ever get point farmer
Never send points out, always expect your team mates to give you points, if not yell at them for not sharing
These are the only items I've ever bought, The only thing I really type is the !sp command to send points out.
Tell people to ask for points and be prepared to send them out.
A majority of every player on GC spawns in the same spot, knowing these spots on every map might just make you a better player.
Like specialK once said, its all about pre-aiming, but not just that, you also need a good reaction.
Maximum volume with a good pair of headsets will let you know where infected(and what type of infected depending on the sound they make) are before you see them, so aim in the direction of the sound and just wait till they show themselves.
Its easy to farm points as infected on certain parts of every map, with certain types of infected, but some times it can be hard. I will not give any advice on point farming as infected.