Paper Planner
I have a simple monthly/weekly planner that I got for $8 at Target. I write down major events like due dates and exams in the monthly, so I can see everything important that's coming up. I also put a post it with my goals for the month on the monthly page, so I can reference that quickly. I write daily tasks and to-do lists in the weekly section. If I have something that isn't given a specific day to complete, I write it on a postit note that can move with each day. I cannot stress this enough: write in pencil. Things come up and you will need to erase to make space.
Google Calendar
I preprogram all of my repeating events in my Google calendar. I also add any events that are at a specific time, once I know them. The Google calendar allows me to see my day spatially, instead of as a long list. And it helps me determine how much free time I really have to complete my regular tasks.
An example of how I do this:
My current monthly (July) has the following events: birthdays, paydays, doctor appointments, dinner/coffee dates, appointments with PI, phone interviews.
The post it has: write academic statement, write personal history statement, email more POIs, finalize grad app list, plan honors thesis, finish reading current meta-analysis papers, student for the gre general and bio.
My current weekly (starting July 22) has the following events in their respective pages: the daily chapters assigned in my gre practice books, submit timesheets, clean the rat cage (needs to be done every 5 days), skype meetings, when my lab group is at the greenhouse, coffee date, and write academic statement.
The post it has: remember ti exercise, drink water, keep up with literature, and smile.
I used to use all electronic, but I really like to see my week laid out in front of me, as well as my month. I can get that better with paper. Also, I am often in the field, so I need something that won't lose battery or reception.