Balance the equation of the neutralization reaction, making sure there are equal numbers of each atom of both sides of the equation. Consider, for example, the neutralization of sulfuric acid: H2SO4 + KOH --> K2SO4 + H2O. On the left said, you have three hydrogens, one sulfur, one potassium and five oxygens. On the right side, you have two potassiums, one sulfur, five oxygens and two hydrogens. Adding a two in front of KOH -- H2SO4 + 2KOH ---> K2SO4 + H2O -- evens out the potassiums, but now you have both an extra hydrogen and oxygen on the left side. Placing a two in front of water on the right side, however, counteracts this: H2SO4 + 2KOH ---> K2SO4 + 2H2O. Now, you have two hydrogens, one sulfur, six oxygens, two potassiums and four hydrogens on both sides.
Calculate the number of moles of acid you're neutralizing, keeping in mind that one mole of a substance is equal to the number in grams of its molecular weight in atomic mass units, or amu. Using the periodic table, you can see that sulfuric acid has a molecular weight of 98.06 amu: two hydrogens at one amu each; one sulfur at 32.06 amu; and four oxygens at 16 amu each -- 2 + 32.06 + 64 = 98.06 amu. If you have 150.05 grams of sulfuric acid then, you would calculate moles as follows: 150.05 g H2SO4 x (1 mol H2SO4/98.06 g H2SO4) = 1.53 mol H2SO4.
Multiply your moles of acid by the coefficient in front of water in the balanced equation to get your moles of water. The neutralization equation for sulfuric acid, H2SO4 + 2KOH ---> K2SO4 + 2H2O, tells you that for every mole of sulfuric acid you add, two moles of water should be produced. Since you added 1.53 moles of sulfuric acid, you expect 1.53 x 2, or 3.06 moles of water.