I think the first thing you need to do is make a list of what you will be using the shed for. Note the sizes of things that you will want to store and move through the door of the shed. ie if you are moving a 54" mower through the door you do not want a door that is 36" wide. Remember junk fills the space, so consider all possible future uses. If you don't have a bicycle now condition may change such that you will need to store them in the future.

Next look at the work flows for those items. You will want some type of work bench. again permanently attached to the building or free standing.

Finally estimate the square feet you need in a shed and its configuration. Lofts are nice as it gives you a lot of storage, but you also must consider shed height. You do not want to be working in the shed bent over or banging your head every time you turn around. From the height and loft angle. a barn (gambrel) roof shed is much better that a gabbled or flat roof shed.d

For my shed, making a list of things was simple, as one came with the previous house we owned. This not only gave me an idea of the square feet I needed but the arrangement, ie side entry or front entry.

Several times I have made a drawing of the shed and the items that are to be stored there. I then move the item around in the shed drawing until I get some thing that looks like it would work. Don't be afraid to rearrange the shed after a couple of years use.

Once you have done all of the above you can then start looking for plans or suppliers. I really consider building a shed myself. (I have construction experience) But after considering building it myself, buying a prebuilt shed from Lowes, etc or having a local company build it on site; I decided that from a cost and quality perspective the local company was the best options. Note: Cost considered not only the cost of material, but also my time in doing the project. For me it would taken several weeks to complete the project. The local company arrived in the morning and finished it that day. The shed was a gambrel roof and 10'X 12" with lofts at each end.