Slugs and snails eating lettuce?

Question

I have been trying to grow lettuce and I am having some problems with what I think are slugs and snails, Something appears to be eating my lettuce and it is not growing much. I was wondering if anyone could confirm that this is the work of snails, and recommend any strategies to stop the snails. The lettuce has been growing from about mid winter to early spring (Southern Australia)

Photos (click to enlarge) These two photos show the lettuce plants.

Any tips or help would be appreciated.

Update

The lettuce has started to grow a bit more. I think that although snails and slugs might have been eating it, it was probably mainly the cold stopping it from growing.

This being said, Tyler K.’s advice in the accepted answer is very useful to anyone with a similar problem.

This is what the plants are starting to look like now (same plant as first photo):

Answer 1

Very well looks like that could be slug/snail damage. If you have a small amount of lettuce plants then just going outside at night with a flashlight and hand pulling off plants and the ground will be sufficient. Or putting a small cup full of beer will attract and subsequently drown them. This is probably all you need.

I grow a lot of lettuce and different greens on a scale where that's pretty impractical though. I use Iron phosphate which is OMRI certified organic slug bait and killer and it has worked very well for me. You just sprinkle a little around your plants every so often and that area will be mostly slug free.