Any advice on painting a room a deep red?

Make sure the wall you are painting is in good condition.  Prepare it really well first.

I have a few dark coloured walls and find that any minor imperfection becomes very apparent on a dark wall.

As suggested, good quality paint and rollers will also help. 

I would use primer. If you get your paint at a specialty paint store I would ask the person who sells it for a primer recommendation.  My inlaws had good luck with dark red over primer.  Post photos when you get it done!

The best advise I can give is don't skimp on the paint.  Buy the best quality you can find.  We painted our home theater a very dark red wine color and the ceiling a very dark blue.  It took two coats and both came out perfectly. http://wrightideas.typepad.com/expirationdates/images/htcouch_1.jpg

 

We had no issue painting two of our rooms a dark red.  We used a regular old white primer and then two coats for Ralph Lauren paint, available at any Home Depot.  We used Townhouse red (a deep dark brick red) in one room and Pomegranate Red (a slightly lighter, brighter red but still dark) in anther room.  The paint is expensive but worth it for the results. 

http://www.danabushman.com/here_is_the_house/2007/02/tile_extravagan.html (fifth photo down is the Townhouse Red)