I do weigh myself everyday,in the morning. If I don't, I can get off track with my eating. I know I gain about 2 pounds over the course of a day, and that is normal for me. It is gone the next morning. I used lose a couple of lbs. after a long ride or work out, but that doesn't seem to happen any more.
I also know by the feel of my clothes. At my height (barely 5' 1") even an ounce makes a difference. Then I cut back on high glycemic carbs, wine, etc.
I lost about 6 lbs when I was sick last fall. I got back to my regular weight around the end of December (it was nice to be told to gain weight), and now I am taking a medication that has weight gain as a side effect. I noticed I had gained about 5 lbs. when I got back from vacation, despite 4 days of strenuous x country skiing. So, now I am really watching what I eat. I've lost about 2 of the pounds, but it's pretty hard for me to lose weight under normal circumstances. I've weighed around 105 for most of my life since high school, except for when I was teaching aerobics and I got down to 90 . I started gaining in my late forties and that's when I started cycling.