This year was a flop for my tulips. So I guess it's time to dig up, divide and replant. Is there a time that it's best to do it? Any tips? I've never done it before.
Most modern hybrids of tulips do not multiply. Most tulips are only productive (flower-producing) for four years or so, then they peter out and just throw up small leaves every spring until they finally die off. This is natural, and not something you are doing wrong, or can be improved by adding fertilizer.
Modern tulips (as opposed to "species" tulips) are something that need to be re-bought and planted every few years to get the optimal display.
Well, there are still older varieties around that do perennialize fairly well at least in some areas (especially the North). How long did you have these tulips, s6bee? And do you know what variety or the source? If there is some chance that they are *not* one of the Fancy Modern Hybrid Type Things, it might be worth lifting them and seeing what you've got, and maybe dividing them slighlty if you see where they want division to happen, and replanting them in some out of the way place just in case they feel like growing back.
Chances are, though, that it's what Laura says -- time to go shopping
Basically, you put your shovel in far enough away that you don't risk slicing the bulbs in half (this is the part where i tend to have trouble with daffodils, lol), lift and expose the bulbs, and see if there are any natural divisions where the bulb is producing a large daughter bulb. If so, just snap it off and replant. I do not know about tulips specifically but daffodils occasionally degenerate into a whole bunch of pathetically small bulb scales / bulblets, each too small to flower. In which case all you can really do is separate them out, toss all but the largest, replant 'em and wait several years for them to reach blooming size again.