The easiest way is to find a recipe that produces the ABV you are looking for. More fermentables = more alcohol but you need to keep things balanced. Some extracts are more fermentable than others so SMALL sugar additions can sometimes help. IPA's tend toward dryness so a small amount of sugar is ok (5% or less of grain bill).
Something is always fermenting....
"It's Bahl Hornin'"
Kegged: Sour Saison, Pale Ale, Aggie Ale, Firestone DBA, De Koninck Blonde
Bottled: Belgian Quad (Grand Reserve), Derangement (Belgian Dark Strong)
On Deck: Pliny the Younger