- filling out the values in the corners
- setting lines where there are adjacent 3s
- setting lines where there are 3s diagonally (including cases where they are only separated by 2s)
- clearing everything around 0s and filling in the lines (if there is only a unique way).
Between them I still only solved like 25% of the board. The rest of the board is usually either empty, or only contain 1s and 2s, from which I cannot really deduce anything. In these cases I usually resort to guessing a line, and trying to trace whether it results in a contradiction eventually, so I can cross it off, but this doesn't seem like an optimal solution.
Are there additional strategies that I can use to continue solving the puzzle?