Because a garden shed is essentially a prefabricated, prebuilt structure arriving in easy-to-handle bits it relies on its own component parts to give it stability and not a foundation. This makes its location very flexible.
The key thing is that the shed needs to be located on a stable, flat surface preferably a porous surface so that water does not site itself underneath. This can be a problem particularly if your garden is undulating or even on a slope. Digging out is always possible but can be hard work and will probably need a number of other considerations to be taken into account such as: what to do with the soil?, Is it creating a low point that will fill with water in a storm?, etc. An alternative is to build a suitable size ground level platform, effectively flattening out the lie of the land by going up rather than down, the ideal material for this is decking.
Think about what is going in it….
If it is going to store the children’s bikes or maybe wellington boots you will need to ensure it is as close as possible to the back door, otherwise it just won’t get used. If however it is primarily a garden potting shed for storing garden tools and maybe bringing on seeds then the obvious place is by the garden vegetable plot.
Depending on the style of shed being chosen it might be you want the shed to be an actual feature of the garden, an inviting destination that could have a key position. If the shed is purely functional and not that attractive then it could be away from the natural view of the garden maybe behind a high planting of shrubs or a trellis.
A shed can be a large object that obscures a view. It is well worth remembering that often there is space under the canopy of trees or a large hedge; pruning out a space for the shed to go will not detract from what you are seeing and will free up what was effectively spare space.
If you are looking at positioning a shed in a relatively small garden the traditional spot would be the bottom right or left hand corner. This might be the right space but you will always see it, a trick would be to bring it much closer to the house on one side or the other so actually it is no longer in your sight line from the house.