Ranges have a lot to do with

1 - How the player has been playing
2 - The coordination of the board

The laggier, the harder to put a range. Pay close attention to showdown hands. This is where you gain a lot of information. If you can't remember exactly how the hand went, look up the HH. You may notice things like

1 - Oh he raised 5x bb preflop instead of 3x and he had a large pocket pair.
2 - He had a draw and check raised, I remember him doing that earlier
3 - He slow played here with a big hand

etc etc.. Reads really come down to hands like, when you have AQ and are raised on a A 3 6 board. There are players I will be playing with and I know I have the best hand. Sometimes when I am in the pot with villian and am getting raised/called I slow down because of how they have playing.

Start with 1 table. Really concentrate. When reads come, you can try mutlitabling... but I highly advise against multitabling without being able to get decent reads on people. You're not going to be able to read everyone, but it helps.