Brew Your Own magazine link have a very interesting article on head retention.
Every edition, they publish some content on their website, and this is building up to a very nice resource.
Have a browse through the article index, I am pretty sure it is called foam.
If anyone is looking for some web based browsing, this is definitely a site worth spending some time on.
Never had a problem with my ag brews, they always have a nice head.
Like the others have said, start getting some more malt and hops into your recipes.
Licorice won't help your head retention. It is available from home brew shops and is usually used to add some different flavours to dark ales and stouts.
Overcarbonation is a different problem again. You need to make sure your beers are fully fermented before bottling. Leave them in primary for two weeks, double check the sg is stable, then bottle. Don't use carbonation drops, some brands are notorious for problems. Buy a sugar scoop from your homebrew shop.
If your carbonation levels are fine for the first three weeks or so, then they slowly start over carbing, you probably have an infection problem.