Wot he said

And don't be afraid to experiment.

There's hundreds of painting tutorials online, covering hundreds of different techniques and effects. Some are really superb, others not so much (too much yapping, overly technical explanations).

For me? There's but four things you need to get to a decent tabletop standard.

1. Even undercoaf. Spray cans are your friend here!
2. Neatly applied base coat colours.
3. Washes and a suitable brush for applying (right tool, right job)
4. Some skill in drybrushing - a technique which whilst really quite simple, take a little practice to get just right.

GW's painting video are good - they move at a reasonable pace, making them easier to follow. The lighting and camera angles are likewise good for seeing exactly what they're doing, how and where.

And the top secret fifth tip?

Patience. Very, very few of us go from NooB to Golden Demon in no time. Put advanced techniques on the back burner, and take your time getting your confidence up on the basics