What information on an antibody product information sheet should be checked before antibody purchase?

To secure the success of experiments with antibodies, information provided about given catalogue antibody should contain the following: 

Host
The host, in which an antibody of interest has been produced is crucial for a choice of a correct matching secondary antibody. 

Clonality
Antibodies can be poly or monoclonal or recombinant. Each of these antibody formats is offering various advantages and disadvantages. 

Antigen
Full length protein (purified from tissue or recombinant) or a short peptide can be used to elicit a given antibody and determines to which proteins such antibody is going to bind. The process of antigen design is shortly described here. 

Species rReactivity
Antibody reactivity to a protein from a given species, should be confirmed experimentally and can be also predicted based on sa equence conservation. 

Applications
Each application requires ispecific validation and product information sheet provides us with a guidance which applications has been tested so far. Recommended dilution provides a guidance for further antibody use. 

Application examples /Validation data
This section should contain detailed protocol describing how a given antibody was used. In case of Western blot technique, it should provide us with the information about: extraction buffer, protein load/well, mebrane transfer type and conditions, incubation buffers, blocking buffer, primary and secondary antibody dilution. 
In case of immunolocalization, the information should contain at least type of
tissue, fixation, blocking and primary and secondary antibody diltions. 

References 
For newly released antibodies, it may take 1-2 years before any publications are available. 

Antibody validation process is explained here.