justifun,
Get the I-129 filed ASAP. Do it online. Once you do it online, you will have a little bit of time to get your evidential paper work together and sent in. The CRITICAL part is that you GET THE I-129 APPLICATION IN BEFORE THE TN EXPIRATION DATE. In addition to that, by doing it online you will have a little bit of time to get your paperwork and act together.
Next, get all of the information you need to support you case. I have (had) letters from Professional Engineers supporting my claim as a Scientific Technician (Engineering) and a variety of other related references.
Also, get your credentials evaluated by a Foreign Credential Evaluation service. I use
http://www.fis-web.com/ and they will evaluate your transcripts and work experience. You may want to talk to them and explain what you are looking for in order for them to determine whether you will fit in the category you need. No point getting an evaluation done and finding out you have the equivalent of an Arts Degree in English Lit, when you need something computer related. While the The Real Canadian indicates this is usually for H1-B's you are trying to make as strong a case for yourself as possible.
You need to make sure you have a solid package when you send it in.
Also, was the post secondary course a two year condensed course? ie: full time all year long? The key to this is perhaps showing the equivalency through the Foreign credential service.
Also, put a solid resume together. While the resume does not need to be considered for TN at all, they always looked at mine.
And last and most - DO NOT LEAVE LEAVE THE COUNTRY UNTIL YOU ARE APPROVED!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Don't start with the family reunion crap or someone is getting married that we always hear. If you leave and get denied coming back then you get what you deserve. WebTiger's deal is something totally different - he got caught up by incompetence by others that were out of his control.