Every board on PuzzleComb gives way to five ideas. None of them is a guess.
Reading the numbers
3
Numbers are block lengthsA "3" means three filled cells in a row, somewhere in that line.
2 1
Blocks keep their order — and a gap"2 1" is a block of two, at least one empty cell, then a single.
4
Start with what's certainA "4" in five cells can sit left or right — but the middle three are filled either way. No guessing, ever.
Five techniques
7
1 · OverlapSlide a block hard left, then hard right. Cells covered both times are filled for certain. A 7 in ten cells always fills the middle four.
3
2 · EdgesA filled cell on the border is the start of the first block. If the clue says 3, the next two are filled too — and the cell after them is empty.
2
3 · Finished blocksWhen a line's blocks are all placed, everything else in it is empty. Mark those cells ✕ right away: they unlock the crossing lines.
4
4 · Gaps too smallA gap of three cells between two ✕ marks can never hold a 4. Cross the whole gap out and the block has fewer places left to hide.
9
5 · Big numbers firstLong blocks overlap the most, so they give the most certain cells for the least thought. Scan for the largest clues before anything else.