Here are few tips to increase your success rate :
1) Do not use captcha tools like GSA captcha breaker or captcha sniper as they cannot break recaptcha and most of the sites are heavy recaptcha dependent. Use death by captcha to solve captchas.
2) Title - Always use short to medium length titles - Maximum of 8-10 words. Any longer and submissions will fail
3) Description - Write only 2-3 lines of description as long or short descriptions are rejected
4) Tags - Enter a maximum of 3-4 tags where each tag has two words only. Maximum rejections happen because of short or long tags.
5) Use multiple accounts rather than just one for multiple websites. If you bookmark 10 sites on one account then majority of your bookmarks will fail. Rather use one account for one project and then other for another website.
6) Wait for atleast 2-3 hrs. between multiple bookmarks on same account otherwise you risk losing that account.