How do you sell in-house training to other companies?

Dear Nibal, I believe the best way to sell in-house training is to sell the value of this training rather than actual training program.
In other words, market the training program based on it's intended benefits that the companies can achieve.
Referrals are an added selling technique.
Solidify your sales pitch with numbers that show how other companies have benefited with your training program.
Additionally, do some research on your customer and relate the program to their specific needs.
I hope that answers your question.
Regards Tahir

Dear Nibal :As a B2B sales, in-house training sales should include the sales fundamentals, that is: -find the major influencer as well as the real decider in the customer(this takes some time) - create very very good first impressions and establish good relationships with the prospective customer -understand the customer and its needs what the customer needs and what you can really do for him -know your competition and your customers competition as much as you can -do not be very pushy(it is a consultative style of selling -be active member in institutes, other organisations as well in internet forums ,where besides the new connections that you'll find there also ask the managers of these clubs and forums to present a part of what you sell by giving a free seminar or webinar to the clubs members -ask for for a "very short!!" presentation of your product and company=power-point -have patience and perseverance! -add all these to what Tahir supports in his answer Always to your disposal Ted Spanos

To answer this question , I would say you need to explain the realistic results which benefits the participants and the ( Company ) and make employers perveive and realize that . 
Then clearly explain  who needs it, when, how, and for how long.

In my opinion it is always wise to take a top to bottom approach. Seek the permission from the top person to study the present scenario and to revert with feedback as to how your training program can add value. If one is hesitant to approach the authority, then position some one senior from your end to make an opening. In this meeting with the top person make sure that the message goes down the line about your approach. The top to bottom approach is effective as the contacts below the authority will be attentive/opened and free to provide information to you. You will experience minimal hurdles and objections at all levels irrespective of the functional areas.

Here I would like to support the answer by Mr. Tahir, Techniques and interests of the companies are the most important to brand your vision.

We can start with our presentation , our resume , Find a list of customer that we want to offer our products , and send our presentation , we can invite them to see how we work , we should make a list of5 strength that we have not all of them and inform our customers ,

Selling is a marketing strategy, Show your superiority plus other companies who are benefited from your services, references may also a good marketing selling technique.