Vector,
Time estimation is difficult for a majority of people. There are many ways to get better at it - I would recommend David Allen's "Getting Things Done" book (You can look up on amazon or your preferred vendor). While you may be a little put off by the 'corporate' exterior, it boils down to being a time management book for everyone.
As far as making plans - here's a few rules of thumb I go by. Your experience may vary, but if you're starting with nothing, this will be a step in a positive direction.
1) Whatever you are doing, if you do it with a single other person, it's going to take twice as long. When in a larger group than that, it's going to take 2.5x as long, minimum. See math? Yuck, I know . But if it takes you one hour to get dinner at some restaurant, getting it with a group of six is likely going to take 2.5 hrs (due to people being late, not being able to get a table, etc.).
2) Starting right now, double your travel time estimates to get anywhere. Most people grossly underestimate travel times. In your case, you've already said you get lost easily ( I do too...) so I think this will be a very positive step for you.
3) Since you are in university, schedule studying in 3 hour blocks. You'll never really get anything done in shorter blocks- really they should be longer but I realise that's very hard to do sometimes.
4) If you are going out - to a bar, club, etc, always assume that it will take the rest of the night, no matter what time you start. Do not try to make plans with more than one group of people, unless everyone from both groups has agreed to meet at a set time/location.