How to Solve a 7x7 Hashi
Start with the islands that leave no choice: a 3 in a corner with only two neighbors must send at least one bridge to each, and a 4 there takes two to each. Draw those bridges, update what the neighbors still need, and the small grid usually follows island by island.
Three Levels on a Small Layout
Easy puzzles only need counting. Medium puzzles add the connection rule: a bridge that would lock two or three islands into a closed group is impossible. Hard puzzles sometimes need a bridge imagined, followed and ruled out.
A First Bridges Puzzle
With few islands and short bridges, a 7x7 puzzle is the right place to learn. Draw the bridges with a ruler or freehand, and use a light pencil mark for a bridge you are not yet sure of.