I have this problem sometimes. I'll tell you what I do. First let me say I am NOT the most organized person, but it can bite me sometimes, so i just keep it simple. I make my schedule for the next week late in the week (Thursday or Friday.) I always ask my patients about next Dr. Appt. and make a note of it so I know to not even bother with that day. Usually I'll even plug them in on the following day on the schedule and tell them I'd like to see them to follow up on their MD visit, get new orders, med changes, etc. Then I look at patients who have regular orders (wound care mon/wed/fri, infusions that have labs every Monday) and I fill those patients in first. Then I take into consideration acuity level, visit pattern, last visit, and of course location (lol) and fill those patients in.
I always call patients the night before to schedule the appointment, unless I'm swamped and I don't get home from work until after 8, but sometimes when that happens I just stop and take a few minutes to call and schedule. Some agencies I know call same day, and it's great to have the flexibility to do that last minute but I find on rare occasions I don't schedule the night before I'm almost begging my visits in. If I don't get in touch with someone (and it's not an ordered visit for labs or what have you) then I fill them in with someone else who is conveniently located near my route who actually answers their phone and move that person to another day. It doesn't take too long to figure out who never answers their phone and then I just leave a message "Mrs. Smith, it's the nurse, I'm planning on seeing you tomorrow between 10-11." Sometimes I get there and they've gone out to the hospital, but if they're one of those that never answers there's no way to know that and oh well it happens.
There's always those new admits that take longer than expected, but I mostly manage to avoid those visits you think are going to be in and out and you get there and find out the patient fell two days ago so you need an incident report and yesterday they went to the PCP and he decided to change all their meds around and they're holding a Spiriva playing with it saying "how do you use this thing?" because they're going to spill all that when you call to make the appointment so I know ahead of time to schedule a little bit of extra time to deal with all that. I can normally manage to stay within the arranged times though, and the patients are there expecting me.
Oh and did I mention I REALLY dislike having a bunch of "oh no you can't come until after 11" at the same time.