If your garden shed currently has no source of electricity and you plan to have an electrician add an electrical supply to this structure, you should heed the advice offered here.
Make sure you're happy with the position of the shed before letting the electrician begin
Most garden sheds do not have the same deep foundation that a house does; instead, they lay flat against the top layer of whichever surface they're placed on. This means that they are relatively easy to move around. However, after the electrician connects your garden shed to your house's electrical supply, it will not be as easy to change the shed's position. Doing so might involve having to ask an electrician to disconnect the supply before moving the shed and then getting them to reconnect the wiring again.
Because of this, it is best to ensure that the shed is in a location that you are happy with. If, for example, if it is currently in an area where lots of tree leaves end up falling on its roof during the autumn and you dislike having to remove lots of the leaves from the roof throughout this season, then you might want to put it farther away from your garden's trees. Similarly, if it is pressed up against your garden fence to the point where you cannot access the shed's rear panel, then you might want to pull it away from the fence so that when the time comes to do repairs on this panel or the fence behind it, you can perform them without having to disconnect the shed's electricity so that you can move it and reach behind it.
Think carefully about what electrical features you want the electrician to fit
Before you call up the electrician, you should think about what specific electrical features you want them to add. You might, for example, want to add a couple of plug sockets, rather than just one, if you'll be using the shed as a home office or if you do a lot of landscaping or DIY that involves the use of power tools. Likewise, you might want to ask them to install not only an interior overhead light inside the shed but also some exterior lamp lights on either side of the shed's door so that it's easy to unlock or lock the door late at night.
If you don't take the time to really consider what electrical features you require before booking the electrician and only realise that, for instance, you want some exterior lights on the shed after the electrician has arrived, they might not have the specific materials or tools needed to install that particular feature and you might then have to arrange for them to come to your property a second time to fit that feature.