If you shop at local markets then your meal plan will be pretty seasonal by default. Tomatoes, onions and garlic are all good purchases since you can make so many things from them. Whole wheat spaghetti for example is healthful, filling, and not too ambitious!

You might look through back issues of the magazine "Everyday Food" (they actually just stopped printing paper issues and are now exclusively online) to see their feature that's all about menu-plannning for a week. What's nice is that they give you five dinners AND a grocery list. The approach is pretty creative -- you'll feature the same herb in a few dishes so you (1) only buy one and (2) actually use it all. There's also a lot of smart shortcuts for leftovers, like using leftover roast chicken in a soup a few nights later (but usually more clever, to be honest). I think that looking at a few issues will probably inspire you to get some ideas. But it's definitely seasonal and budget-friendly if you buy and use everything in a few simple, healthy dinners.

I'll tell you what I do myself....
I check out a site such as http://www.eattheseasons.com/ to find out what produce I should be getting at this time of the year, then I replenish my staples (potatoes, rice, bread, condiments, onions, garlic, etc). I choose what kind of proteins I should get by watching sales (steaks and ground beef in the summer, hams and turkeys and roasts in fall/winter, salmon/lamb in spring etc).
Then I try to make a plan where I get a few new recipes I want to try (weekends), a few meatless days (pastas, burritos, etc), one craving day (whatever I've been wanting bad), one soup/sandwich day (I have a dozen different recipes), a fun food day (pizza, burgers) etc.... you choose your own, and voilà, easy menu planning.

Similar to the above comment - I have a CSA year round and the farm emails me a couple of days before I get a new box to tell me what is going to be in the box. I then make a meal plan around that. Since it's winter I eat a lot of soup. I also often make a big pot of some type of beans a couple times per week and use them in soups, salads, veggie burgers etc.

There were some great posts here on Kitchn last year about meal planning, with LOTS of helpful tips from both the editors and the user comments. I recommend searching back for them. Definitely inspired me and got me more organized--got me started using Google calendar for my meal planning, which has been really helpful.

Keep lists of vegetables and fruits by season and consult those when you're grocery shopping. Don't buy anything that isn't on that list.

I second this recommendation! I have recently been clearing out my backlog of food-related magazines, but I refuse to let go of my collection of back issues of "Everyday Food" - I have them organized by season and will delve into them for inspiration when I'm doing my weekly menu planning. As Lmj816 says, they're quite creative and seasonal with ingredients; everything in each recipe is readily available a a reasonably stocked grocery store; and, best of all, the recipes ALWAYS turn out well! Can't beat that!

I have had those weeks when my menu plan reads like a restaurant menu--a new and fab dish every night. It's fun, but it's exhausting and impractical. I'm breaking myself of the "oh that looks good" meal planning habit by focussing on my pantry. I bought millet to make a granola recipe from thekitchn? Fine. Now I have to use it up before I buy another grain. My rotation is now less varied, but it's healthy and it's easier.

I try to plan about one fancy meal a week (cooked Monday or Tuesday so I have a chance to use up leftovers/extra ingredients later in the week), then for the rest of the week I do easy basics. My favorite dinner is a giant pan of roasted veggies, with either chicken thighs or salmon - I can switch up the veggies enough to keep it interesting.

@Lmj816 - That magazine sounds great! I will definitely be looking into it. Thanks for the tip!

For me, it was an easy thing to figure out how to purchase seasonal local foods. But I had a hard time getting interesting and different recipes. That is, until I subscribed to www.eatyourbooks.com. You can try a free mini version. You register your books, and then when you get 20 lbs of zucchini, you can easily find those recipes (hidden in your books or on the web) that call for zucchini. Its been a tremendous help for me.

I only allow myself to cook one recipe a week that calls for more than 3 ingredients that I don't have. The only exception here is produce, since I try to buy that fresh every week. All the other recipes I make have to include things I already have in the pantry, fridge, or freezer.

Also, as much as I hate it, I don't even save/pin recipes that have ingredients that I can't find at my normal supermarket, even if they sound like the most wonderful recipe ever. I will never make them even when I have the best intentions to drive an hour to the asian market to find that one item or whatever.

Eat local = Eat Better!