I tend to make a main path with some offshoots that lead to other areas. If people travel through the forest I'll usually have an easy path to follow through it, since human habitation means clear-cutting and road-making. I'll have little branching paths that aren't easily visible sometimes - grassed over edges of the map and such that are hidden by trees, which become animal paths that lead to other areas. Usually I block off all edges that don't teleport you to another map in my maps, so the player can see that if there's a part where they can touch the edge they're likely able to find another area that way.
Cabins or caves for resting in if the forest is longer. Maybe even a small town or village in the middle of the forest (or a camping spot), so that there's a safe place to sally forth from.
Sometimes if I want a more maze-like forest (untouched by human hands for thousands of years, for example) I'll make it very overgrown and loop in on itself at times. You'd naturally find shortcuts here and there, though they'd likely be guarded by harder enemies. Also making a shortcut is fun - say there's a cliff part where you can jump down to a lower layer of the map that is closer to the entrance or the like. I also like sharing screens with different parts of the map so you can see that there's a path that you'll get to in the future and can kind of map some places in your mind (oh, I saw that to the south there was an area past the river I could get to but I haven't found a path to that going east. Maybe if I go west I'll find it instead.)
Lots of dead ends, small clearings, and sometimes even incorporating things like cliffs, caves and other different kinds of landscape helps a forest feel a bit different and interesting too. Landmarks (or at least recognisable areas) so that the player can orient themselves based on what they remember (like, oh, this is the part with the lake. if I go north from this area it'll lead back around to the waterfalls and west of there was a cabin).
Depending on the game there might be hidden paths.
Oh, something else I always (or almost always) do is have small cutouts of trees. See I usually use the canopy forest to map forests with, but a sea of just black is boring, so I make little parts that show the trees breaking up a bit to add variety.
For example:
The blue are the different exits. You can see that the southern one is a bit harder to figure out as an exit than the other two. On the left you can see an inaccessible cut-away of the forest to give the feel of there being more than just the path. Overall, the red is the only part you can walk, making a larger map feel more cramped by cutting off areas to go.