Definitely use Champagne yeast - lasts longer because it's designed to survive high acidity and alcohol levels, also foams at the bottom instead of at the top so less chance of yeast in the tank.
Definitely add a little Baking Soda - it buffers the solution so it takes longer for the solution to become so acidic that it kills the yeast. How much you need depends on the hardness of the water you use.
Tips: Keep your yeast in the freezer so it doesn't die. It will take several hours for it to get going.
Don't use water that's too hot! If it's too hot, it will kill yeast! You want the temp between 70-90°F. If in doubt, go for cooler, it will just delay the activity of the yeast a little.
Don't use too much yeast! Less is more, I used only 1/8 tsp of Champagne yeast for a 2-liter bottle. Also, keep the sludge at the bottle as there's live yeast in there.
Cold room = slower production, warm room = faster production. You'll always get more CO2 during the summer, you may want to warm the bottle if it gets really really cold where you live in winter.