I work in HR and have represented my company and my friends on occasion. A few tips from my experience:
Make sure that you have complied with the Tribunal's orders and directions eg exchange of witness statements and schedule of loss etc.
Hopefully the other side will have prepared a bundle of documents. The Tribunal will work from this. Know your way around it. The Tribunal will only read the documents that you refer them to, make sure that you refer them to all the key documents that you are relying upon for your case.
Be prepared - prepare your questions for the other side's witnesses based on their witness statements - at least as much as you are able and you will also need to react on the day and may need to make changes.
Be organised - keep your documents in the bundle in page order. Flag the key pages and highlight the sections that you particularly want to refer to.
Don't be afraid to ask for a few moments to gather your thoughts when required, but don't overdo it either.
You will have to stand up and swear on your chosen holy book or take an affirmation before giving your evidence. You will then be expected to read your prepared witness statement. Pause whenever your statement refers to a documents so that the Tribunal members can read it. They will tell you when to resume. You will not be able to take a marked copy of your witness statement onto the stand with you, you will have to use the copy that was given into the Tribunal clerk.
When facing cross examination be prepared for hostile and leading questions eg "I put it to you that you didn't do that did you?". When you are asked a question, answer it honestly, don't be evasive. Don't answer a question with a question.
A Tribunal can be a stressful and emotional time for many people. The Tribunal willtry to put you at ease but it can still be daunting. If you have not already done so, I would recommend that you try and visit the Tribunal for a day in advance of your hearing and sit in on a few of the cases. They are normally heard in public and you can wander in and out. It will help you get a feel for how they work and what to expect. It may help put you at ease and feel more confident.
Whether you win on not will depend on the facts, as they come out during the hearing and the relevant law. Emotion will play no part in the decision. Try and focus your case on the relevant facts and the relevant legal points.
Whilst the Tribunal makes its decision based on facts the press are only interested in sensation. Threatening to involve the press is only of value if your former employer is shy of publicity and you are hoping to settle before the hearing. I would not recommend involving the press for any other reason. They are unlikely to present an accurate account of events and you may not like what they print.
Good luck.