One week before my month ends I like to lay out the new month and pre-plan everything, sometimes I get a little bit too stressed about it because of the amount of things I sometimes have, like April, was quite a stressful month, but not everyone is like that.
Back to the subject, I found that taking my time and doing it on a clear mind, it's actually better, because I can program things properly, rather than popping one on top of other and trying to fit everything in a couple of days.
I found a system which I think works for me, of couse I'm still making changes and figuring what works and what doesn't but overall, this are the tips that have worked best for me.
Have a layout, if you read my resolutions, you would know that I like to set monthly goals, those go on my monthly page, something I look back too every week or so, to remind me and add books, series or movies that I might have finished those days.
Visualise your calendar, I use Google Calendar and I like to add dates, appointments, meetings as I schedule them, that way I can see them when I'm planning my month, but also as I pre-plan my week, I try to check it often, sometimes even once a week, if for some unknown reason I add my dates on my diary (Usually happens when I have to make changes or add things on the day that is going to happen), I like to add them at the end of the week, I like to compare them and make changes on one or the other.
Leave free time, I've been there way too many times, when pre-planning don't think that you'll magically appear in places, leave free time in-between things, that way you won't stress and you won't feel bad if something you didn't plan shows up.
Write down with pencil and when it's done go back with pen, this is another common mistake of mine, for some reason I like to think that everything is going to go according to plan, but when it doesn't I found myself hating the fact that I decided to write it down with pen and I hate crossing things and making it look ugly, so what I do is, write mostly my dates with pencil and either that day or at the end of the week, I go back with pen and make it look pretty.
Add due dates, I'm guilty of forgetting to pay some things, I like to add them and have them present at all times, that way I can programme it and not be rumbling around trying to fix my mistake.
Do it monthly, weekly and daily, you just read what I like to do monthly, but every week I like to go through everything an extra time, add things I didn't at the time, compare calendars, add last minute things and pre-plan my next week, I usually do this on a Saturday night, and every day I like to go through, make a to-do list and see what i'm up for the next day.
Some overall tips would be to take notes, add extra information and things you might forget, those always help on busy days when you tend to forget what everything was about. Have fun with it, make a layout that works for you but that also makes you happy looking at it, this is not something that has to be bad, just something to help you be more prepared and do more.
Another extra thing I like to do when pre-planning, it's to clean, to put everything back on it's place, take garbage out, change what needs to be changed and just refresh everything, that way I can start with a clear mind on a clean place. You just have to learn what works for you and enjoy it.