When you know the recipient’s name, sign it “Sincerely yours” or just “Sincerely”, or in the US “Yours truly” is acceptable. Don’t try anything more cutesy or friendly unless a) you know the recipient quite well and are certain you can be informal without seeming disrespectful, or b) you have a “trademark” letter ending that’s part of your public persona (and the talent and popularity to pull it off). Signature and printed name: Signing your name is a minimal assurance that you stand behind what was written.
Since your signature is likely to be difficult to read, type your name down a couple of lines so that your reader knows who is writing to them. Enclosures: (Below signature block) If you have included any further material _ a business card, a brochure, a price sheet, whatever _ list the number of items and describe each. Finally, proofread, proofread, and proofread again. While a friend might excuse even the worst spelling and grammar, a business letter is often your first (and maybe only) chance to make an impression _ it needs to be impeccable.