I think you will find I have already answered. But here it is again: I have taken no steps so far to help mitigate the effects on my business of a no deal Brexit. Now please educate me.
It's just common sense really. It isn't, as I first thought, you who are importing the goods you sell. Therefore you need to speak to the importers; your suppliers? They should be researching;
The likely amount of any price increases to them.
The likelihood of delays to their deliveries.
If they, like you, have done nothing you could approach other suppliers (if there are any) to see if they're more proactive.
Failing all that, the WTO website lists tariffs, which will give you an idea about price rises. Clearly customs checks will delay deliveries so that needs to be taken into account.
If you have regular customers who order from you, let them know that they should order earlier than normal and perhaps recommend that they order extra in the meantime if the product keeps.
If your customers are one off, and you have a website make sure you have a page on Brexit, warning of any future price rises or delays as a result of a no deal exit. (Is that a Nexit lol?)