1 X 4's - 8'
2 X 2's - 8'
2 X 4's - 8'
4 X 8' sheets of MDF or plywood, 3/4"
A ton of wood screws
The amount of each is determined by how many and what size you need your shelves.
Determine the area you have for the shelving and buy the materials necessary. You will be able to determine how much you need, once you read and see these instructions. You can make your shelves as high and as deep as you want.
I will describe how to build one unit and you can expand on this to suit your needs.
To start with, cut two 2 X 2 to the height you require. Screw the 2 X 2 on to your wall where there is a stud. Most studs are 16" apart, so screw the second 2 X 2 to the next stud, 16" apart. Now cut two 2 X 4's to match the height of your 2 X 2's. Now you can determine how deep you want your shelves. Lets say you need a 2' shelf. Cut your 1 X 4's into 2' pieces. You will need enough 1 X 4's to cover the height of your shelving unit. Once you have cut enough of the 1 X 4's, you will have to pre-drill the 1 X 4's on each end to prevent splitting. You can make a drilling jig to space your holes just right.
Now that you have all your material ready, you can begin the construction. Starting at the top of the 2 X 2 mounted to the wall, screw in your first 1 X 4, using two screws. At the front of the 1 X 4, screw it to the 2 X 4, using two screws. Make sure the first 1 X 4 is level and the rest will be level. Screw another 1 X 4 on the other side of the 2 X 2 and again to the 2 X 4 making sure this is level as well. You now have the start of the support unit of the shelf. Continue to screw 1 X 4's on each side until you reach the bottom. Space the 1 X 4's an inch apart. This is done to accept the shelf itself. Once you have your first support completed, do the same to the second 2 x 2 that is screwed to the wall. You should never go all the way to the ceiling with your 2 X 2's and 2 X 4's as you will want to screw a permanent shelf to the top for stability. A 7' shelving unit should have about 16 1 X 4's on each side, again spaced 1" apart.
Now that you have your two supports built, secured to the wall and a top permanent shelf on the top to square the unit, it is time to cut you sheets of MDF or plywood to make your shelves. For this simple unit you will need to cut pieces that are 2' by 15-1/2"s. Cut as many as you require. Once they are cut, you simply slide them into the support units between the 1 X 4's. You can adjust the height of the shelves by moving the plywood up or down in the 1 X 4's
Although these instructions may seem a little complicated, the pictures will show just how simple it is. You can leave this as a single unit or expand across your wall, using the studs to determine the width of your shelves. I wouldn't go more than 4', and at 4', don't put anything too heavy of the shelf. You can leave the wood raw or paint it. If you want to use these inside your house, you could use oak, maple, walnut, etc.
You can now start to store you stuff and move the shelves to fit whatever you have from paint cans to ski's. If you have any questions, please do not hesitate to ask.
Thanks for looking.