Go to your Minecraft config folder, mine is at %appdata%/.minecraft/config
Look for the file called tiersystem.cfg
Open it with your favorite text editor, such as notepad or notepad++
Change the tier count to the number of tiers you want on your pack
Change the thingsToKillForTiers line to have the name of entities to kill to unlock the next tier, use spaces to separate entities. An example is in the config. If you are unsure about it, go to the en_us.lang file for the mod you want or for Minecraft. Look for the entity.<mob>.name line. What is between entity. and .name is what you want to use.
Change the tierRestrictions line, how you change it depends on your version of Minecraft. For Minecraft 1.6.4, each line is a tier, put the item/block id(s) of the item(s)/block(s) you want to restrict. Metadata is set by putting a colon, ':', after the id. Different items are separated by a space. For Minecraft 1.7.10, it is much easier. Each line is a tier, for restricting an item/block, put what you would use for the /give command. Each item/block is separated by a comma, ','.
