How do I select the right secondary antibodies?

When selecting secondary antibodies, it is important to take the following factors into consideration:

• Host species in which the secondary antibody was generated – Always choose a secondary antibody that was generated in a species different from the primary antibody host and target species. If you’re using a primary antibody that was derived from a rabbit, then you must select an anti-rabbit secondary antibody that was generated in a species other than rabbit. 
• Targeted reactivity – The secondary antibody that you use must be able to detect the intended primary antibody target. If you want to detect a rabbit polyclonal antibody, you’ll need to use an anti-rabbit secondary antibody.  

Other sources also include many other factors to consider when selecting a secondary antibody such as: purification, cross-adsorption, multiplexing, antibody class and subclass, whole antibodies vs. fragments, and conjugates.