Be wary of training pros who are not interested in learning all they can about your products, processes, people and overall business strategies. Avoid having the instructional designer do all the grunt-work. Generally, the more you can provide in the way of information, case studies and examples, the more on-site vendor expenses are saved. While any training developers worth their salt should able to create good training, you will save time and budget if your designer comes to you with knowledge and experience in improvement methodology. Avoid rush jobs.
Most vendors boost rates for quick turn-around projects.
You may get the training when you need it, but the training may show the scars of long hours or inadequate preparation. Avoid unnecessary content changes. Experienced instructional designers are masters at helping teams nail down ambiguous requirements. But if you are outsourcing your curriculum, bring the vendor into the strategy sessions early. Strive to get content agreed upon by the team in order to avoid last minute major revisions.