After choosing a domain extension, you must choose the name itself.
Choose a short name.
It is recommended to use a hyphen to separate words, to make the name more readable for Internet users and to improve search engine optimisation.
However, there is no point in purchasing a domain name consisting of a plethora of keywords.
It is a good idea to use a brand name or trade name.
Check before that the name is not a registered trademark.
Consider reserving the most obvious variations, such as adding or removing a hyphen between two terms, plural or singular forms, etc. Example: www.skirtsonline.com or www.skirts-online.com. This will prevent the unpleasant surprise of seeing a competitor's website appear with a domain name that is too similar to yours.