For online play all the above is great. An even better and certainly more complete explanation on hand reading can be found in
this threat.
For live play I always try to look for the classic tells (from Mike Caro), but also blinkrates and where people put their hands when waiting for you to decide. What really bothers me about Caro is that he often interprets uncomfortableness with bluffing, while some people are uncomfortable holding a huge hand. Keep this in mind. Also many people that have seen Mike Caro's videos (or read his books) know these tells and will reverse them. Don't fall for this. How and especially where people place bets on the table helps me a lot as well. Some people tend to say how much they bet a lot when they are bluffing ro holding a weak hand and are mostly quiet when they're holding the nuts. I could go on and on, but I'd advice you to watch the DVDs by Annie Duke (How to beat the big boys) and Mike Caro (Pro poker tells). That will be more than enough to start out. They won't help you at first, but you get to recognise a lot of these tells slowly while you practise at it.
A final tip: Start observing the players to your direct right and left at first. Than add the loose players at the table, because you are playing against them most often and they are probably the players you are going to win the most from. You can't possibly observe them all at once.
GL