Alright huge Starwars fans listen up, this applies directly to you!
I have been to conventions and so many people dressed up wanting to be their characters want to act like them, now I'll admit I haven't gotten into the whole lightsaber thing yet but I have done bokken/bokuto fights with people on various occasions and that includes big Starwars fans but one thing a lot of people do is spin. now spins are only appropriate in a few occasions:
1. Intimidate. - Used at the start of combat before blades have crossed, however if there is enough distance, or if you both are getting ready before sabers actually cross. on that note, if they can do it too than it had no effect, and if they challenged you odds are they are not completely pushovers. With that said... just because they confront you if they can spin and you cannot, it means nothing about their skill do not let it intimidate you.
2. Finisher - you won and you want to look cool.
3. Gauging distance and momentum of your weapon to use it to your advantage (Advanced) - do not use this unless you have practiced this kind of thing for years, and even then I don't even suggest it for a slight miss calculation can cause your loss, but sometimes it helps and also if gauged properly creates a false opening but more on that later.
Next is stance.
I find a lot of people do dramatic cool stances, I admit they do look cool... but are not good for use. They tend to leave you open. Now I'm not going to tell you the stance to use since its situational and martial arts have been disputing these kinds of things for years, so who am I to say what stance suits you? but when picking or developing a stance:
make sure your knees are not locked and your body relaxed, be sure to hold the center and try not to have any openings.
FootWork.
Footwork is Key. When it comes to sword arts, everything you do is from your body not your sword, and is reflected a lot in your footwork.
Never leave your feet. this makes you vulnerable. keeping yourself planted makes it harder to lose your balance.
Consistency. not in the sense of being "predictable" but in the sense of not being random, practice and train a form that will keep you steady and reduce the chance of fumbling.
In Thrusting. or other advanced moves, always plant your feet solidly (and don't lock your arm) the force of the impact should travel through you and into the ground where you solidly where standing. Also during advanced moves its easier to react if what you had intended goes wrong, and you need to switch motions or change strategies (its a counter-counter =p)
(on this note I want to point one one thing to you Kendo-ka saber fencers. do not be afraid to let your left foot cross your right, if you have to take a step its better to take it than to be off balance and/or do an awkward move and get yourself hit or makes you fumble.)
(thanks to my Jm419 who helped with the structure of this section.)
Holding your Center.
Find the center, hold it own it, control it. If you can do that you will win! A lot of people I have went up against have had weak or wavering control of the center, do not waver.
To go a bit more in-depth: Starwars fans Specifically do dramatic long/far swings leaving them open in the center. Someone controlling the center can easily take advantage of such a wavering control.
Swinging.
now I don't know about the rules of your matches that you do... but I assume hitting any part other than the head and neck is legal (ALWAYS STOP BEFORE HITTING THE NECK AND TELL THEM THAT THEY HAVE LOST! YOU COULD SERIOUSLY HURT SOMEONE! in fact unless you know what your doing, don't even go for the neck!) other than the groin for guys *nods* that's just dishonorable (waist just above is fair game though)... and a worse target than you'd think xD. (unless your going 3 rounds and you want to pull a karate kid but again dishonorable.) Anyways joking aside you can use this to your advantage, most inexperienced sword fighters would not know how to control and stop before hitting, and so they will hesitate. train to have a decisive swing so that you may A. not have this problem B. use the hesitation against them.
Grip. This depends on your style a lot like stance. I do Japanese sword arts and so my wrists are turned in. admittedly don't know all the mechanics of all different styles and who am I to say whats better for you. (This however is a very important thing, like footwork however again I cannot tell you whats right for you.)
when Swinging your saber. remember to keep your shoulders and body relaxed, a lot of people tense up, and that could be the end of them.
with that said make sure your strikes are decisive other wise they will have no effect. however even though your body should be relaxed, somewhat tighten (maybe tighten is the wrong word) feel the power in your stomach, your core, and strike with that power.
Things to Train (for starters).
Train to understand timing of yourself, your opponent and even the world around you. (good life skill)
Train your peripheral vision, see everything without looking. (good life skill)
Remember to breath! if you do not breath you fatigue faster and you don't think strait, when blocking or striking breath normally.
Tactics (some may be to advanced or locational)
Control your Opponents weapon.
Create controlled openings, let them think they can strike and finish you, but don't let them.
Create paths that allow them to move somewhere freely, but control where they willingly go.
Keep the sun in their eyes and to your back.
Never move back!
Do not think of defense... there is no defense, think of defense for the sake of opening up to strike offensively.
There is more that can be put, and I will update this. I hope you enjoyed this and remember Train hard Day and Night and then you will start winning all your saber duels along with RL combat ;p.
a book I recommend is the Go Rin No Sho (book of five rings) almost any version is decent, just make sure its not a business book, still helpful but not as specified to this. (this is not an advertisement)