Originally posted by Lizking 
No sir, I have ruined my fair share of meat.
(But I am always willing to learn and eat brisket) 
 Did you cut it right out of the smoker without letting it "rest"? That will dry it out very quickly.
I 
highly recommend this article on brisket preparation and smoking. The guy knows his stuff and it works well. You will always get good results with it. He's got the time and temps down about perfect I think.
And.. once you have a good system, it's a great place to "take off" and start experimenting with you personal variations to develop your style.
He covers about every aspect:
Brisket Defined 
Choosing A Brisket For Barbecue 
Prepping A Brisket 
Seasoning The Brisket 
Temperature Of Brisket Before Cooking 
Converting Collagen To Gelatin Is Key To Tender Brisket 
Cook To 180-205°F Internal Temp 
Where To Measure Internal Temp 
 Cook Fat-Side Up Or Fat-Side Down? 
Turning & Basting 
Temperature Plateau 
Foiling & Resting After Cooking 
Slicing & Chopping Brisket 
Burnt Ends 
Brisket Yield 
Leftovers  
Brisket Selection & Preparation