Do an inventory of all the tools, supplies and everything else that you want to keep in your workshop. If you have duplicates of tools, excess supplies or anything that you're not going to need very often, either throw it out or put it into storage somewhere outside of the compressed amount of space you have available in the workshop.
Install a pegboard or other tool-board with movable hooks for hanging tools. Hang as many tools as you can on the wall to make more room in your drawers and cupboards. Organize the board by tool type and then by size so that you can quickly find whatever tool you're looking for.
Put a small garbage can near your work area and empty it frequently. This keeps trash from accumulating on your bench.
Buy a tackle box, small workshop storage unit with several drawers or use a series of empty coffee cans or jars to keep all your nails, screws, nuts and washers organized by type and size easily.
Create clear areas for the different types of products you need to keep in your workshop, but remember to think vertically instead of just horizontally. For instance, in a cupboard, you might dedicate one shelf to holding all your paint cans. However, after you put your paint cans in the cupboard, if you see that you still have vertical empty space above the top of the paint cans, you need to take advantage of it. Install an extra shelf in the cupboard and put all your brushes and rollers on the new shelf. Always try to use as much vertical space as possible in a small space.