Your headline does most of the work
The headline appears next to your name in search results, comments and connection requests, and LinkedIn search weighs it heavily. 'Software Engineer at Company' says little. A role, a specialism and an outcome, written with the words recruiters search for, gets you found.
You have 220 characters. Use them for what you do and the result you bring, not a list of buzzwords.
Write the About section like a person
Only the first few lines show before 'see more', so open with a hook: what you do and why it matters. Write in the first person, give one or two concrete results, say what you're looking for and end with how to reach you.
Keep it true
The writer only uses the experience and numbers you give it and leaves [placeholders] where a real figure would make the point stronger. Recruiters check, and a specific true result beats a big vague claim.