Heres some handy hints on keeping the paint where you actually wanted it.
The Wire Trick
Stretch a fine gauge wire across the paint can and twist ends around each side of the handle. When painting wipe the brush on the wire. This prevents the paint from messing the can or falling into the rim or down the side.
The Tape Trick
Wipe the rim of the paint can. Then wrap with masking tape, leaving one edge as a lip. This will allow you to pour more smoothly and also prevent the paint from clogging up the rim, leading to ill-fitting lids.
To prevent the bristles of the brush from splaying, clean the brush, smooth the bristles down, wrap in paper and tie with a rubber band.
Plastic Bag Trick
When using a roller tray, flecks from old paint that has remained on the tray can become mixed with new paint. To prevent this from occurring simply put a plastic bag over the tray.
Keeping Paint Smooth
For water-based paints, pour in sufficient water to cover the surface of the paint by about 5/10 mm. Then close the can. This will form a seal and prevent a skin from occurring.
For oil-based paint, the same idea applies, but use a glass of mineral turps instead.
If you follow these tips you'll not only find painting easier but also less expensive!