Organic material such as compost is the best thing. If you want to use sand, use it sparingly and use "coarse builder's sand". You can find it in Home Depot near the bagged cement mixes (inside the store at mine).

Two kinds of bagged compost at Home Depot - Composted cow manure and mushroom compost. Mushroom costs more and naturally people say it is better. Another product is "soil conditioner". Very fine particles of ground bark, one brand name is "Nature's Helper". A cheaper alternative is the "top soil" at Lowe's - looks like the same product to me and is half the price.

Clay is really not all that bad. The ability to retain moisture is helpful - avoid the crispy hard surface by using a good layer of mulch - hardwood, wheat straw, grass clippings, pine straw, pine chips .... That will keep the surface from excessive drying.

Yes, the slope and the fact that the bed is raised will both help with drainage.

Good luck!

This is all subjective topic, so expect a lot of opinion. I'll share mine.

1) Don't bother with sand. Personally, I'd say it's a waste. Why bother?

2) I would buy enough compost to fill up to within 2" of the top, and plan for your bed to be raised at least 12" from the top. Multiply HEIGHT(ft)xWIDTH(ft)xDEPTH(ft) to get the cubic volume needed (in feet) to fill the area. Add 1-2 cubic feet onto this (for amending the clay). Personally, I like just using "Moo Nure" from Home Depot as my poop blend of choice.

3) Doubt drainage will be a problem. If you're worried about it, mix couple inches of tiny pebbles and rocks into the bottom of the hole after amending the soil. Drains should not be necessary if you follow #2.

4) Squirrels can be kept away with cayenne pepper sprinkled on the soil and reapplied after rainshowers (supposedly, my DW swears by it). Plants that repel pests and help other veggies grow based on how they interact with soil - this concept is called Companion Gardening (click here for articles on the subject). Great concept, and it works.

5) You'd be amazed what a weedeater and a pair of loping shears will do. Once you cut it all down, continue to mow in that spot regularly throughout the year, and it should prevent the brush from coming back.

Some tips: After you build your bed, dig up the first 2" of sod/grass/etc. inside the bed (before you add soil/manure/compost). Take a tiller (power or hand tiller), break up the clay, toss in a couple bags of manure, then till that into the soil and rake it out. The goal is to mix the soil and clay so it's not just straight clay. The manure is going to entice earthworms and other creatures to come up from the ground, which will further breeak up the clay nearby. If using regular untreated wood, DO NOT put it near your house. Termites love untreated wood, and if you don't like termites in your house, don't put untreated wood that comes in direct contact with the ground anywhere within 10' of your house. If you use treated wood, I would recommend to line the inside of it with black tarp (4mil thick) so you don't see any of the pressure treating chemicals leeching into your soil (which are much less harmful these days than days of yore). A staple gun will hold it to the inside - DON'T LINE THE BOTTOM OF THE BED OR YOU WON'T DRAIN! Just keep the wood from touching the fill soil.

I amended my beds by digging out the clay and then mixing back in 1 part clay, 1 part mushroom compost and 1 part Nature's Helper.

I like to plant a border of marigolds around my veggie beds. It helps with bugs and keeps neighborhood kitties away. I love cats but I don't like them spraying my veggies! The marigolds work like a charm.

RE: the squirrels, I love my Yankee Flipper feeder. My squirrels have finally made peace with it and they are content to sit underneath and eat the scraps the birds drop. The Flipper is expensive but it has paid for itself because I don't go through near as much seed.