Make a note of possible plots, plots you maybe gave up on a long while ago due to lack of time. Re-read your archives (after a thousand strips, even dedicated fans forget certain details, so the author certainly will) and look out for twists that you could have followed up on, but didn't, or loose plotlines that were left trailing. Incidental characters who could have a greater part to play, people who could resurface. Then pick them up again. Ask friends who read your comic for inspiration, whether it is dumb or otherwise. You don't have to do exactly what they say, but after so many years in the business you should be able to recognise a good idea when you see it, and extract it, capitalise upon it. Make subtle references back to previous strips for dedicated readers to find - reward the reader who pays attention. Chicks dig that. (It works for The Simpsons.)
Try getting two or three potential plots and try to find some creative way to bung 'em together. I find that just the mental hurdling required to mash together two stupid plots involving King Arthur and a tube of Plutonium flavoured Pringles (that's an upcoming plot in StickManStickMan, those of you who read my comic) can provide endless inspiration - as well as a secnario sufficiently crazy to pay its way with gags. And if you're thinking of adding twists, then think at least a dozen strips ahead.
Pretty much the same goes for jokes. Something funny happens? Write the thing down. When writer's block comes, and you know it will, dig out your gags archive and do some intermission one-off gags, and you're set for another week. (Of course, if you're using up gags daily, you might not ever get an archive like this. But I find it works for me.)
This post is aimed at all comic strip writers, not Greg. Note: Some or all of the above may be complete rubbish.
