Tag and description for website

I have been getting a pretty low CTR in google for my website, i am sure that this is because of bad tag and description. I have tried different tags and descriptions, but still don't have good results, how do you create a good tag and description for your website or maybe you have examples?
Thanks a lot.

I usually do a keyword research for my niche, so i can figure out which one is the highest searches keywords with less competition
If you're using wordpress, you can also optimized your content with all-in-one seo.