Internal meetings  are usually to teach or reinforce company ideas, in addition to being team building events. Your primary goals are simply to show up, listen, and interact. Your measure of success is how well you retain and apply the new information, and the relationships that you strengthen. 

Internal meetings are private, but events such as conferences or conventions  are open to the public, including potential vendors, partners, and customers. You might be there for new relationships, or to attend workshops. If you have a booth on the show floor, or if you're giving a presentation, you'll be a spokesperson for the company. In short, you're likely to have multiple goals when you go to an event. 

Scouting trips might be to check out potential locations, employees, or markets. In scouting trips, your goals are marvelously specific. Bring back the local information or signed agreements, or job applications, whatever is needed. The important part is that you get things that are only available by visiting. 

Sales trips are to move customers through the sales funnel, while service and maintenance travel is to support existing customers and company functions. For these trips, specific quotas or instructions define your goals well. 

Finally, there is professional development, typically involving daylong seminars or similar training. Here your ability to remember and apply the training speaks for itself. 

No matter what kind of trip you are taking, keep an eye out for serendipity . That is, the opportunities that occur on the spot and that you couldn't have predicted. That is especially true at events, which are dense with possibilities, but it is also true in other type of trips, like for example professional development trips. The student next to you could lead to or even be a new business opportunity. So remember to exchange your LinkedIn links, collect business cards and hand out yours. 

At the same time, don't let serendipity get in the way of the trip's goals. A sales pitch in the middle of a professional training could just disrupt the event, and ultimately serve neither purpose. To really understand your goals, talk with your manager or client to understand why they want you to make this trip. Now, you might have to press them a bit on this because believe it or not, they might not really have thought about the "Why" very deeply. But again, if they don't specify goals, there is no way to measure a trip's success.