got serious about digital painting sometime in '04 - '05
As for tips, here's a few tricks i use;

There's two buttons on your tablet pen, under your tablet properties, reset them to keys you use frequently.
ex. I changed mine to the [ and ], which are the default keys in photoshop that make your brush bigger or smaller. A buddy of mine set his to Alt, allowing him to quickly switch over to the eye dropper when he's using the brush tool.

Under the Brushes tab in photoshop, click on Other Dynamics and change the opacity and flow jitter to Pen Pressure. I find doing this makes playing in photoshop a bit more like real painting.

When i first got into photoshop i found these tutorial's very helpful: Steel Dolphin

The best advice i can offer though is to constantly find other digital art you like and try to do it yourself, mimic their style or color scheme, figure out how you can duplicate whatever it is you find cool in their work - its a great way to evolve as an artist and pickup new tricks

www.conceptart.org is a great place for inspiration

Eh, its all fun though, i'm still learning =D