I see that no one better has responded yet :LOL so I'll try to give you a few pointers. I just started menu planning a few months ago, and I've found it really really helps, not only in spending less money, but it cut eating out and made sure we had some *decent* every night for dinner.
What I did is: I gathered my cookbooks, recipes, etc and sat down in front of the computer. I made a list of all the things I normally make (generics like tacos, spaghetti, etc and my "specialties"), then I searched through cookbooks and foodnetwork.com and allrecipes.com for new ideas (I still do this regularly when I'm tired of the things we eat). I started off small, with about 20 or so dinner ideas and have worked up to probably over 50 in my list. I make my menus for 14 days (payday to payday). I put all the "main dish" things on the list, then under each name, I list each and every ingredient that I need to make that. I also think about what side will probably go with it, and put that in there too (unless it's something like a plain vegetable or a salad). I even went so far as to organize my list into groups. We're omni's so I have a section for chicken, beef, pork, vegetarian, fish/seafood, etc.
When I get ready to make my menu plan, I sit down in front of that "database" of meals and pick things that jump out at me. A lot of times, I've had something on my mind I want to try or make for a special occasion. I do a computer-generated calendar. So I put a list of the meals I want to make at the bottom. I start putting them into the calendar based on things like how long it takes to cook (BIG dinners are usually sunday when DH is off work). Now I do once-a-week cooking, though, so it all gets made on Sunday. Anyway, I try to alternate things so that we eat chicken about every other day, and turkey or fish/seafood in between. Occasionally we have pork or beef. Meals that are heavy or fattening, I try to make sure the next day we have something light (a big salad, for instance) and that we don't have two types of potatoes close together. That sort of thing, I'm trying for variety in our diet.
If I have holes, I go back to my list and search for things to plug in, like a light pasta after a meat loaf or something like that. It works great for me, and we don't feel like we're eating "bad" so much (I don't make a lot of really heavy things anyway, but you get my point!)
After all the meals are assigned to a day, I get my list and go through and write down everything I need to buy for each meal. That way, I know I have every ingredient on hand to make all the dinners and there's no last-minute shopping trips (except my second trip for more fresh produce and milk). Then I just add in the "staples" like flour and milk and such.
This is sort of rambley but I hope it helps! Good luck