It can be so hard to get things going, especially if you are depressed. I would first identify if there is a reason for the depression that is external (death of a family member, ending a relationship, bad grades, etc). If it is an external precursor, then you either have to work through it or walk away from it as applicable. If the depression comes from within (and sometimes, that is just how it is), then you can do a few different things to help yourself.
First, drink enough water. You don't have to force yourself to down 64 oz a day, but make sure you're having something on hand "most of the time" for sipping. Limit drinks with caffeine, like coffee and soda, and also those with lots of sugar (or worse, High Fructose Corn Syrup). You don't have to give up anything... but keep it to a minimum.
Next, get some sunlight. A daily dose of natural sunlight will help you as much as some medications (provided you aren't clinically depressed, which is another thing entirely and should be evaluated by a doctor). Even five minutes of driving with the window down and the sun on your skin will be helpful, and the longer you're able to do it, the better. I personally have a "sun lamp" that I use through the darker part of the year, to help me with my own depression.
Eat healthy foods. Again, you don't have to quit eating out or avoid all fast foods or anything drastic. However, working to make sure you get one healthy meal a day can go a long way. Leafy greens are great for those with depression, and if you don't like them in their natural form, consider using powdered greens in soups and stews, so they're "hidden vitamins". Eat foods that you know the origin of (ie a tomato as opposed to a sauce in a can) whenever possible.
Go for a walk. Play Wii with your kids or friends. Stop at the pool after work and float around for a bit. Do something you find fun. We have the "dance party" games that we do with our kids on the Wii, and it gets us moving, and it's funny, and we all enjoy it (and sometimes we play it after they go to bed lol). Doesn't matter what you're doing... just do *something*.
Treat yourself. Get a facial, or have your nails done (or do them yourself with or without a girlfriend). Take a really hot bath with your favorite bubble bath. Read (or re-read) a book to get your mind engaged. Get offline for a while (online can be great, as evidenced by blahtherapy itself, but can also suck you in and eat time and energy in negative ways). Just do something, anything, for yourself. Start small.
Invite someone over. When I'm having a hard time motivating myself to get dressed or eat, I will invite over someone. I know that I don't want to be caught in a long tee shirt and nothing else, so I'll slap on a skirt and a blouse, just to be decent. Then that feeling of clean clothes on dirty skin will get to me, so I'll shower. And it moves on from there.