1. Estimate Bearing (in case map is upside down)
In winter you tend to use a small laminated map and you’re often being battered by winds etc so hard to focus. It’s very easy to take a perfect bearing using the compass (add/subtract 5 degrees as it was back then) but *not* realise you’re holding the map upside down and your bearing is 180 degrees out. You’re focused on aligning the compass body with the grid lines etc.
So, the solution is to guess the rough direction (N, S, E, W) etc in your head based on your rough knowledge of the area, eg We should be heading NE back to the ski area. Then when you take your bearing and it comes in at 150 degrees, you can go ‘hang on, that doesn’t look right’…..
It’s probably a bit winter mountaineering specific, but still a good sanity check.