checklist for clock changes

Hello.

Could you point me, or give me some suggestions about a checklist for speed clock change. I mean....I changed the fuse to have the clock at 1Mhz....but then....

if I upload the the sketch with the F_CPU set to 1000000L, all seems to be not working. For example the serial connection works intermittently. If I compile with the old 16000000L F_CPU, serial works, but delays commands seems to be not working. I'm missing something for sure...

So, do you have (or do you know where can I find) a checklist I should follow after changing the fuses? Something suggesting the change I have to do to compile, the functions that I need to review and so on....

Thanks so much....

cips