Question for the good people here:

I often fall into situations where I am successfully dating a girl, but I don't know how to schedule future dates. I find I am most successful when we plan our next date during the current one. Sometimes when it it not possible to plan the next date (due to conflicting schedules) I'll tell her I'll call her, but I never know when to call. sometimes I take a few days to call and I feel like it shows that I'm not interested. What do you do? (Note I always send a "Had a fun time :)" text at the end of the date.