I tend to charge a day rate - in Germany that seems pretty normal and I charge at about the going rate. If the client is more price sensitive or has a very spec

I tend to charge a day rate - in Germany that seems pretty normal and I charge at about the going rate. If the client is more price sensitive or has a very specific task in mind then I do hourly. I track all of my time for myself (including invoicing, admin, side projects etc.) but I don't expose any of this directly to clients, this really helps me figure out which clients and projects are worthwhile and which not. Fixed price has never worked out well for me but that's not to say it can't work for everyone, as a sibling comment explains it requires very specific requirements and contractual agreements, if you are going to go fixed price I'd recommending setting yourselves some minimum price that you won't go under. This helps to filter out a lot of the work you don't want to do.