I'm always searching for that one key thing that will help me be more organised in my day to day life. I read lots of organisation books and I'm always asking other professional people what they do to stay on top of everything. So this is a culmination of all my learnings.
My first step when I'm feeling overwhelmed or unsure where to start may actually seem counter intuitive but I clean my work environment. I find if you have a messy desk, messy office, messy files on your computer it makes everything feel overwhelming and disorganised. By spending an hour getting your environment around you organised you will instantly feel on top of your game and able to focus on that one key task you've been avoiding.
I've read multiple times that you should always start on the hardest task on your list first. I have experimented with this and sadly it is true. You definitely have a sense of real achievement and satisfaction if you tackle that hard task first thing in the morning. Which in turn frees up the afternoons to focus on ticking all the other minor tasks off your list leaving you feeling more organised and on top of your work load.
This probably goes without saying but if you can action something straight away, quickly, then do so. Don't feel as though you have to add it to the list or schedule it in your diary, because the amount of time it takes to do that, you could have completed the task already.
As Lorraine Murphy (Writer of Get Remarkably Organised) says, think of your future self, would your future self appreciate if you did something now. This could be as simply as preparing your clothes the night before so in the morning you aren't rushing around ironing clothes, looking at weather apps etc. Perhaps its washing and blow drying your hair the night before instead of getting up early to do so. If you can do something now that your future self would appreciate, you're one step ahead.
In staying organised with our family activities including any work commitments, birthdays, our daughters activities, I keep a calendar (formatted in excel) colour coded, printed and stuck on the fridge for all to see and write on. Visually seeing your week or month is very handy when it comes to getting organised, planning and being prepared for future events.
I know Lorraine is a big fan of this one too. Pre planning all your meals is a massive game changer in your week. And it doesn't take that long to do. Grab some receipe books, pick a meal for each week night, write the ingredients down and shop exactly what's on the list. You save money, a heap of time and you don't waste food. Going shopping now without a list seems ridiculous to me. If you really want to save time you can make double quantities and freeze meals for the next night or perhaps next week.
Just these few key tips help me stay on top of everything.