I believe most of these points should be driven by user data, business need and type of application.
Filters depend mostly on the application type. While it's useful at Amazon, not so much at Google, for instance. If there are clear categories, and some common search types might be in multiple unrelated categories ("mouse" in a store that sells both computer hardware and animals for instance), make the filter prominent.
It also depends on your capacity for building a great search engine. In my opinion, search filters are often there to compensate for bad search queries. You should thrive to make filters irrelevant by allowing the user to filter himself, by entering more precise search terms.
Conclusion : no filter, but better search engine.
Best bets are often more marketing-driven. If you sell something, you put the products that make you more money (or the most popular) upfront. Otherwise, it's not so useful.
Moreover, best bets might be seen as ads and completely ignored by the users, or effective only on some category of population. Knowing you user is key here, and analytics are your friends.
"Others searching for this also search for" falls squarely into this category. If your business have an interest in it, put it on the bottom, or at most in the middle by clearly separating it from the rest. However, it's more often relevant to put such things in the item details than in the search results.
Conclusion : if your application/business benefits from it, put it upfront, otherwise, remove it.
Spelling suggestions are fine, but more user-data-driven. Is a popular item hard to spell ? Is there a "popular" misspelling of a certain item ?
In any case, "did you mean" is a great feature to push forward, but you must be sure that it will not annoy users with search suggestions of similar spelling even though their spelling is fine, but for another item.
Note that in the general population, most people are either terrible at spelling, or don't care very much, or don't pay attention. If your audience is more specialized, you might not need it.
Conclusion : if you're capable of providing a great "did you mean" engine, put it upfront, otherwise, remove it.
Search as you type is very helpful, but for that, you must both have a way to display the results that is not obnoxious to the users (does not go over other interface elements that are useful while you're searching), and data for common search terms.