To win a tournament...It really isn't that hard once you've studied the TCG ways long enough. 
One way, is to read every article on every Deck Mechanic's page, read all the recent TCG strategies, and read the Single Card Tips on the pokemon you plan to use.
To me, every tourney winning deck really shouldn't have more than 1 evolution, and SPEED kills.  Unless you're gonna stall for a Venusaur, Exeggutor, Moltres, Etc, You want Speed.  EVERY tourney winning deck MUST have 18+ Trainers, or else the tourney was wayyyyyyyy too easy.  Hehe.
Try to stick with a 4-3 Evolution and basic pokemon, and remember to leave lots of space for trainers.  Remember, Mulligan really isn't a problem, you can just Imp. Oak, if you really have that little pokemon to be Mulliganing FREQUENTLY.
 
Now to Count the Cards.
 
x Basic Pokemon 1
x Basic Pokemon 2
x Basic Evolution
x Stage 1
 
You don't necessarily have to have a evolution, but if you choose the right one, it does help.
 
Energy Count (I'm saving trainers for last, since they take the longest explanation.)
4 DCE
20 Energy 
 
The standard (I know Kitty Fox agrees) is probably 24 energy, it always works.  If you have low energy costs, you can go lower, to the next standard:
 
4 DCE
18 Energy
 
22 also works for Low energy decks.
(Mono-Color decks are usually much more fluent energy type wise.)
 
TRAINERS!
These win the day.
You should always have more than 15, and there are the few that you DON'T use.
Oh, and don't use any coin flipping trainers, unless it's REALLY worth it.  (Like Recycle)
 
The "Bad" Trainers
 
Clefairy Doll
Maintenance (Most of the time, except for Semi-Stallers with Bills)
Pokéball
Potion
PokeFlute
Full Heal
Pokédex
 
The "Strategic" Trainers (those to be used only in certain themes)
 
Imp. Oak
Lass
Super Potion
Pokemon Center
Devolution Spray
Energy Search
Super Energy Removal
Defender
Mysterious Fossil
Pokemon Breeder
Revive
 
The "Good" Trainers
 
Energy Removal***
Computer Search***
Item Finder***
Professor Oak***
Bill***
Gambler
Mr. Fuji
Pokemon Trader
Scoop Up***
Switch
Gust of Wind***
Energy Retrieval***
Plus Power***
 
*** - I think these go in every deck.
 
In MY typical decks, these are Standard
 
4 Bill
3-4 Prof. Oak
2-3 Computer Search/Pokemon Trader
2 Item Finder
1-2 Gambler/Mr. Fuji
3 Gust of Wind
4 Energy Removal
2 Super Energy Removal
2-3 Energy Retrieval
3 Scoop Up/Switch
3-4 Plus Power
2 Lass
 
I know it's a lot, but if you can cram those trainers into a deck, and replace some of them to fit your theme, it'll work out GREAT.  One thing, unless you're a stall deck, DON'T TOUCH MY CARD DRAWING.   : )
This is what a tourney winning deck should look like:  ( well, MY tourney winning decks. )
 
10-14 Pokemon
 
16-22 Energy
 
4 Bill
3-4 Prof. Oak
2-3 Computer Search/Pokemon Trader
2 Item Finder
1-2 Gambler/Mr. Fuji
3 Gust of Wind
4 Energy Removal
2 Super Energy Removal
2-3 Energy Retrieval
3 Scoop Up/Switch
3-4 Plus Power
2 Lass
 
I LOVE TRAINERS.
 
Hopefully, the more people who read this, the better competition there'll be.
Thanks for your time...
 
        -sleepy dragon
 
Hate Mail about my opinion on some trainers go to:
sleepyxdragon@netzero.net  ( and then i'll reply and prove you wrong )  =)
 
p.S.
Win those tourneys!