Select the most relevant keywords or a primary keyword which describe your web page, use easy & the type of keyword which hold the name of the product or service by which anyone can easily reach to your webpage. Use long tail keywords, it is also helpful for you.
To choose keywords for the website, you must use the primary keywords and 2, 3 secondary keyword for your website. You must the keyword planner tool to search the keywords for your website.
There are a lot of factors to be considered when choosing a keyword/s for a website.
First would be the type of business/niche. Second, would be the target market.
Then, how rankable a keyword is. And also, the average no. of searches a keywords get in a month locally or globally.
Google's Adwords keyword planner tool is a common starting point for SEO keyword research. It not only suggests keywords and provides estimate search volume.
based on the theme of the site you're building, for example, you are building a fast food web, the tag might like "fast food is good for health," "Fast Food Delivery" .. this sort