Being a freelancer and having an above average score of replies, invitations and hires I would recommend keeping your submissions to a job short, professional and also something that stands out.
-Don't send the same thing to different clients
-If other people have left reviews see if you can find the clients name and include that in your submission (see if they have any jobs completed by scrolling down below the current job posting)
-Also check their hire rate percentage, if its low that means there's a good chance they wont hire. I usually look for clients with 60-70%+ in hires. Meaning out of all the jobs they post they actually hire too.
-Also keep in mind its just like passing out flyers when using your connects, if you pass out 1000 flyers you might get 10-20 calls, just keep building your profile and portfolio and people will start coming to you.
Good Luck!
