Each and every cover letter should be creafted to the project, not a cut/paste cover letter. I write to the poster, to reach them and let them know I am offering my services and how the process works. I recently won a project because I told the reader in the letter that I wasn't going to waste their time with a letter saying how great of a designer I am. I got the project 5 minutes after sending that letter.
"I have downloaded your required files and viewed your cityscape image and am here to offer my services to you and a quick turnaround. I'm not going to waste your time with a proposal that tells you how awesome of an illustrator I am, I'm here to offer you my services as your request. Let me know and I'll start. I'm ready to start immediately, if your ready to hire me."
So write to the viewer and be short, concise and add samples. Make them WANT to hire you.
I am working on upwork and my skills are amazon, ebay, shopify, copywriting, about a year but Don't have many clients any can write a cover letter for me and also tell me how can i write a best cover letter?
Are you sure that all or most clients make a choice depending on the examples of previous works? We all have a statistic how many times profile was viewed. My experience says me that I can expect number of views about a third of the proposals. To do more great and relevant examples is a obvious think, but works only partly.
re: "Are you sure that all or most clients make a choice depending on the examples of previous works?"
I never meant to imply that.
Different clients look at different things.
Some clients focus on portfolios. Some clients read cover letters. Some clients look at work history. Some clients consider many elements.