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by tel 3742 days ago
Typically evaluation of a Go board runs something like

(1) Identify all the groups.

Most important are any groups larger than about 4-6 stones or groups that cannot be sacrificed for some other reason. You'll often see some straggler group which exists purely to disconnect your opponents groups keeping them weak. That one is small but important!

(2) Determine their status.

Essentially, their opponent decided it was time to kill this group and tried with all their might would the group be able to survive? You can be fuzzy about this ("there are a lot of possibilities for this group to live") or even economical ("it would take a lot of turns for B to kill W's group here, is it worth it?").

(3) Decide who "owns" every empty intersection.

Once you've identified the strong, living groups you'll see that they probably capture territory because they surround some empty intersections. These spaces can be invaded or reduced if they are too large (so that the opponent could possible attack inside and make a living group) or if they have open spaces (where an opponent could threaten to stream inside). There will also be a lot of points in the early and middle game for which nobody really owns and you can evaluate if one player merely holds greater or lesser sway over those intersections.

(4) Subtract maybe 20 points for each weak group that can't be sacrificed.

Saving groups that must be saved is an expensive operation and your opponent will probably cash in on you doing so.

(5) If it's early or mid-game consider each player's global influence.

For instance, a common trade is that one player will make a living group in the corner and take points while the other player will surround that group on the "outside" producing a large wall facing the center. This wall cannot claim to make territory since it doesn't completely control any location, but it certainly makes battles nearby tilt in the favor of the wall owner. This will translate to cash elsewhere for that player.

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Don't try too hard at any step. Part of skilled judgement is being able to do each step accurately (and include more important factors) much in the same way that materiel balance in Chess can be hard to judge unless you know how to contextualize it.

Also note that a well-matched professional game will be decided by just 1 or 2 points. Until your judgement is very tight or the game is very near the end it can be hard to be precise enough to see that.