First look underneath the pots they usually hide there. If you have other animals or children around, slug pellets would be to risky. Try a few beer traps or if your plant pots are sitting on a saucer sprinkle some Epsom salt (never regular salt) in the saucer to kill and or deter the slugs

Well you can, so long as you don't use too many, but its probably better to put slug pellets round the pots - unless you have very large pots with large plants in, the slugs are probably heading to the pots at night, having hidden out somewhere shady and dampish during the day.

You could try putting just two or three pellets in the pot to see what happens. If the slugs are very small and living in the pot they may not venture out to the outside of the pot so experiment a bit.