How do you come to grade coins?

Hello,
I can't judge well between any coins and their grades. How do you actually come to jude your coins?
For example,
There might be a situation, in which you consider a grade, which is not very reliable.
There also might be also a situation in which you prefer UNC grade still having some scratches.
Places with thick flan and some other parts of it might look worn and sometimes do not, which are also a very good chances for a coin be "considered" personally between grades.
Sometimes, a UNC coin might be graded personally as VF or XF just because having a scratch/mark less than a millimetre.
How do you judge grade between your coins?

I see luster and clear features straight XF.
I don't see luster, clear features: VF+
I see luster or not, corroded or heavy scratches or ugly: VF-

Unclear features, good condition: F
Good condition, hard to identify: VG

UNC only for mint sets or shiny coins that you can only find a less than 5% size of diameter scratch on.

XF : no wear is visible to the naked eye
VF : coin has circulated, but only little wear
F : coin has circulated for a long time, some parts are worn flat, details are no longer visible
VG : more than 15% of the design has disappeared
G : you can determine what coin it is
+ or - can be added, but I can't explain the difference between an F+ and a VF-, that's more "personal interpretation"
+ or - effect value for about 20% (depending of course of the difference in value between grades)

Regards
Tony

I see that you have professional rules for grading coins, but the most confusion part is of the flan of the coin, for example, the lower parts of the crown.
P.S. - I hope some of you must have been using magnifying glasses for grading too.

Citeer: "Subha Barua"​I see that you have professional rules for grading coins, but the most confusion part is of the flan of the coin, for example, the lower parts of the crown.
​P.S. - I hope some of you must have been using magnifying glasses for grading too.

​Using magnifying glasses all the time, they should make coins a lot larger !!!

I rarely take the condition of the flan into account, only for high grade coins. Only when there are some obvious scratches or other damages.

A coin can be UNC, but still Xf or VF due to high production or blunt die set.

I use photos a lot when I'm grading. I deal mostly in older coins so seeing a clear example, as close to UNC as I can get, helps a lot. I also look at other examples of various grades and compare my coin to those.

I have:
VG=Lowest. Usually coins from the hardly seeable really used coins or coins with moss growing on them (thats pretty extreme, I only have one coin that has moss on it) to the coins that are almost missing letters.

F=Has wear or dirt but it can be recognized with the first time I see it.

VF= I put alot of coins into the VF category. Mostly coins that arent too used. Its my largest category with 666 coins. They usually have scratches but still shine a little bit (sometimes, usually).

XF=Has been used, but with only a little bit of wear/dirt/something on it.

UNC= Uncirculated, I usually tend to put old coins with for example one under a millimeter long spot of wear into the unc class. Oh, what a sin.

Very nice gradings skills, but I think dirt on the coins is not counted as grade :)

Dirt does not affect the grade but should me mentioned as should nicks and other similar things. Many countries have "official" grading guides with photos, I think those should be followed.