If your app is posting to Twitter using using the API v1.1, it should be able to handle the following errors:
1. This request looks like it might be automated. To protect our users from spam and other malicious activity, we can’t complete this action right now. Please try again later.
2. One or more of the uploaded media is too large.
3. User is over daily status update limit.
4. Invalid or Expired Token.
5. You cannot send messages to users who are not following you.
6. Your account is suspended and is not permitted to access this feature.
For #2, you are probably attaching an image that is beyond the permitted size. In the case of #4, probably the user has been inactive for long and the session has expired. For #1, they are probably posting tweets too soon.