What are the must-follow SOPs? 

I own a small shop in the UK. Since lockdown restrictions are being eased, I would like to know the SOPs that I should enforce on all the customers and the workers of the shop to protect them from the coronavirus. I have seen a bunch of SOPs like social distancing and wearing masks, but I would like to ask if there are any necessary SOPs that we might be missing out on. So if you guys have any suggestions that you have some knowledge about, please mention them.