Do your research. Find out the subject matter of the national seminar, who will be presenting and what participants are expected to attend the event.
Dress the part. Depending on the seminar, you will need to dress accordingly. For example, if you are going to a business seminar you will need to wear professional clothing. If you will be attending a national seminar for little league coaches, the attire expectations will be less formal.
Work on your presentation skills if you are going to be leading a session at the seminar. Make sure you know your material inside and out and have everything planned down to the last detail. Work from a plan, stay on topic and cover all the points related to your subject matter. Be sure to allow time for questions at the end of your presentation.
Study your movements in the mirror. Practice your presentation to see how you present yourself to other people. This may be difficult at first, but it is better you know upfront which habits -- such as cracking your knuckles or tapping your foot -- you want to correct.
Record yourself speaking and assess how well you come across. Like looking in the mirror, it is better that you know in advance so that you can correct the things that may be bothersome to others. Pay attention to issues such as the speed at which you speak and the tone of your voice.
Develop your questioning techniques when you are a seminar participant. Ask intelligent questions which require higher-level thinking skills -- analysis, synthesis and evaluation -- as this indicates you are knowledgeable about the topic being discussed.
Plan to arrive early. Rather than flying in an hour before the national seminar, grabbing a taxi and leaving your bags with the concierge because you are late, try flying in the night before. This allows you to settle in and feel more comfortable in the national seminar setting.
Enter the national seminar wearing an air of confidence because you have done your homework and know you will be able to contribute to the discussion whether as a presenter or a participant.