Solution: Make sure you've escaped things correctly for XML; for example: & should be encoded as &.

Solution: Keep in mind that the order of bindings is important. Once YQL finds a select that satisfies the YQL statement, it uses that one. Try moving the more "specific" select endpoint above the others.

Solution: If you want to use an API that requires its own authentication mechanism, you use the execute sub-element within an Open Data Table to manage this authentication.

Solution: The best way to avoid being overwhelmed is to first look at examples. In general, when creating YQL tables, it is useful to take a bottom-up approach and analyze the result structure of the API(s) that you are encapsulating. First, group together all the services that produce the same result structure. This becomes your "table" or Open Table definition. For each API that produces the response structure, you should create a "select" under the "request" section of the Open Data Table definition. By using this mechanism, you can often consolidate multiple API's into a single versatile YQL table that allows YQL to do the heavy lifting and keep the implementation details hidden.