As a general rule, plant bulbs about three times their own depth and a couple of widths apart, so a 5cm daffodil bulb is planted 15cm deep. Although it is important to plant them the right way up, with their tops pointing skywards, some bulbs, like knobbly anemones, can make this a little tricky. If you're not sure, simply plant them on their sides and they will soon right themselves as they grow.
When planting bulbs in beds and borders, get rid of any weeds and dig in plenty of organic matter such as your own garden compost. If your soil is very heavy, improve drainage before planting bulbs by adding lots of horticultural grit - the one thing guaranteed to make your spring bulb display a wash out is wet winter soil. It's a good idea to cover newly planted bulbs with chicken wire to stop greedy mice and squirrels digging them up again, but this can be removed as soon as shoots appear.
Bulbs planted in pots need good drainage too, so lift containers up onto pot feet or bricks to allow water to flow freely away. Put a good layer of crocks in the bottom and mix in 2 parts compost to 1 part grit before planting.