I weigh myself everyday when I get up (but really... I know by how I feel when I'm getting a bit too portly - I'm kinda portly anyways).
When I'm trying to curb some weight I usually start counting calories and cut myself down to 1500, along with 30min of very rigorous exercise 5 days a week (I usually climb & descend 125-150 flights of stairs in that amount of time). Normally I eat around 2000-2500 calories, strength train every other day, take a Tae Kwon Do class for 2hrs once a week, and get a nice 3-4hr hike in on the weekend.
It depends on your body type too. I'm 6'0" 220lbs. When I'm in peak physical shape I go about 195lbs.
With school starting again soon I don't have the time to cook as much or the money to splurge on restaurants every day - so I kind of cut back on calories naturally in that way.
When I cut back to 1500cal, I usually don't change the foods I eat - I just cut back on the amounts. I usually cut back a bit on the amount of carbs (real easy to eat a lot of calories via carbs), and then monitor my fat and alcohol consumption (which average about twice the calories per gram that carbs and protein pack). When I drop a few of those pounds I'll then slowly increase my caloric intake to my normal 2000-2500.
Definitely watch your beverages. I have the toughest time with fruity, chewy, acidic candy like Mike and Ike's or Jelly Belly Jelly Beans. One "Big Box" of Mike and Ike's packs close to 1000 calories. I'll be munching them over the course of a few hours while doing homework and notice the box is almost empty. I try to only buy the 500cal convenience store sized bag despite the fact that it costs the same as the 1000cal grocery store box...
I had a friend taking nutrition classes recommend that I substitute citrus fruits... sorry... a Mike and Ike candy is NOT an orange section...