When Huck tells Tom that he is going to help Jim escape, Tom offers his assistance (to Huck's surprise). At this point, Tom suggests that both boys contrive separate plans to free Jim then compare their plans. Huck knows that whatever plan he comes up with will be cast aside. Tom's "superior" imagination will win out.
Huck concocts a plan anyway. His plan is very simple, requiring only one night. Huck wants to remove a board from the shack where Jim is being held, have Jim shimmy out of the hole (just as Huck himself did when he faked his death), then run for the raft and take it down-river.
Tom's plan is far more intricate from the outset and it develops more intricacies along the way.
He insists that the escape follow models from all of his favorite prison stories: he smuggles in items past the unwitting Phelpses. He makes Jim sleep with spiders and rats, and write a prison journal on a shirt. He also warns the Phelpses anonymously.
Where Huck's plan is practical and focused on the outcome, Tom's plan is impractical and focused on the "adventure" of the process.
As was mentioned in the previous post, Huck and Tom devise different plans to free Jim beginning in Chapter 34. Before Huck even begins to think of his plan, he knows that they will end up following Tom's plan because Tom is such a "genius." Huck's plan is simple and straightforward. He tells Tom that they would need to retrieve his old raft from the island and steal the key out of the Uncle Silas' pants when he goes to bed. Then, after unlocking the door, they would simply lift one leg of the bed to slip off the chain in order to free Jim. Jim would then use the raft to travel down the river and escape at night. After assessing the shed, Huck suggests that they simply remove one of the boards and Jim would be able to sneak through the hole in the wall.
Tom's plan is drastically different. Tom devises a chimerical plan in order to make Jim's escape fantastic and exciting like in stories he reads. His initial plan is to dig a tunnel underneath the shed so that Jim can crawl out. Tom then thinks they should have Jim saw his leg off to free himself from the chain, but quickly changes his mind. Tom then suggests that they make Jim a rope ladder and have Jim write a journal while they are digging him out. Tom's ideas are absolutely ridiculous, but Huck agrees to go along with the plans anyway.