What Are Your Criteria For A Coin Whether To Grade Or Not?

I don't send any coin to a TPG that has a FMV of under $150...it wouldn't be worth it IMO.
Other than that, I mainly like to have some of my coins in TPG holders, for the long term protection they provide, as well as the resale aspects of my more expensive coins.
I prefer PCGS,NGC,ANACS in that order.

Ill use value as one. I dont have a set price the coin has to be over but try and consider what the value graded would be if it gets what I think and what I paid. If theres a 30+ dollar difference between Ill send it in.

Ill also send things in for a graded set if thats what I need for it.

Most of the reasons will be based on money and value as to why or why not. But if you want it slabbed then its worth it to have it slabbed imo

Yes, assurance of authenticity is a very good reason for submitting a coin for grading. I use ANACS if that is the primary concern about a coin. Another motive is for documenting a specific variety and again ANACS is usually the most cost-effective TPG.

However, value of the coin should always be an issue. It makes little economic sense to pay for grading if the potential value of the graded coin is low. As an example, consider the 1888-O Hot Lips Morgan dollar. I had mine graded by ANACS and they called it EF-45. At that grade level it is worth maybe ten times as much as a normal 1888-O. In the ANACS slab with the variety identified on the label it should be easy to sell for its fair market value. However, if it had been in Good condition it would only be worth a small premium over the standard variety. Since Hot Lips is pretty easy to attribute even in low grade I would not have invested the grading fee for such a worn piece.

Another motive for grading is preservation. Some CCF members have inherited coins with special sentimental value and wanted them slabbed to ensure they were correctly identified and protected from physical damage. In those cases monetary value was basically irrelevant to the collector.