Usually a solo will start out by "making a statement." The idea won't be too difficult to understand or too far out. The next phrase, the one that answers this statement, will complicate things just a little bit. The next phase is "digging in," getting more comfortable and showing a few more things. This might lead to "settling down." At some point there will be a phase of "reaching a climax": more inventive ideas, faster, higher, louder playing. This could occur on the bridge of the third or fourth chorus, depending on how long the solo is. After that, come "winding up," where the musical ideas are often more repetitive and formulaic. The concluding statement might be, once again, a "statement," but sometimes a more ornamental one.
This is not a fixed structure, but a tendency. A very long solo will have a longer settling in or digging in period, or several mini-climaxes. Of course, the structure of the solo can also be described as a series of x number of choruses in a particular for, like ABAC or AABA.
A good solo usually won't be inventive idea after idea, but will have a certain shape to it. Lester Young called it "telling a story." It is a narrative arc. A good player will leave some spaces in there somewhere, too.
An unrelenting wall of sound, like in some of Coltrane's playing, is another option. The song form just opens and shuts very rapidly, and everything is climax. I love that too, but most of what I love is the story-telling.