Tau lists vary in 3 different ways
Mech - army only of -(suits any kind bar broadsides, HH, skyray, pirhana, devilfish, vespid, pathfinders)
Static - many slow 6" movement
Many people who have just started to play pick hybrid and get a feel for which direction they would like to go.
Many people go for Mech/hybrid including units like broadsides and kroot. In my opinion thats probably the easiest list to play with and do well. Pure Hybrid is a tough list to play with, but if you get a good set of tactics (type : fish of fury in google) it is easily the best and most rewarding type of tau list.
Static is a big NO NO, on the tournament scene- you will have to be prepared to give up some of your shooting for moving, as you have to think about deployment and your objectives really hard. This is least sucess full but by no means unuseable. NB: on the rare occasion if your only play sorta annhilation games this list is probably the best.
Units to watch out for- i.e. not very good
sniper drone team (unless its A: a static list and objective grabbing can be given to other units. or B: your playing an annhilation game)
pathfinders (one of the more less useful units in your army, army has to be built around them and that can be disastrous)
Gem units- i.e. hiden quality
A good tau army has to have a good army build.
remember a tau player may be tempted to spam list, i.e. 15 crisis suits, careful with this tau have many vunrablities and this will make them worse. even taking 3 HH's is not as good as 2HH's and a skyray.
when you desider what sorta list you want as for advice! tau have many possiblities armies have to suit the player style or it wil not work
FOR THE GREATER GOOD