Do you mean like a new weapon or armor?
There's patterns.
For example, with armor, Maximum Dexterity Bonus + Armor Bonus = 6(Splint Mail), 7 (Hide, Scale Mail, Chainmail, Banded Mail, Half-plate), 8 (Leather, Studded Leather, Chain Shirt, Breatplate), or 9 (Padded, Fullplate).
For weapons, things get a bit more complex, but in general, a Martial weapon is a Simple weapon with one thing improved by one step (the simple dagger's 1d4 19-20/x2 becomes the Kukri's 1d4 18-20/x2) and an Exotic weapon is either oriental-ish, or a Martial weapon with one thing improved (the Light Mace's 1d6 x2 becomes the handaxe's 1d6 x3).