Things to gather:
Blackberries
Pectin
Sugar (or honey with the special pectin that I bought)
Lemons for lemon juice
8 oz. jars with 2 piece lids
Lots of big pots, bowls, measuring cups, and spoons
Tongs
A funnel that fits into the mouths of your jars if you have one (I didn't and made a mess)
Berry masher (I didn't have one and used a fork, which worked out fine but took time and also made a mess)
Lots of rags and towels to clean up your mess
Your pectin should have instructions inside with amounts of everything. Mine said to use 4 cups of blackberries, but I doubled it.
This is the special Pectin I bought at Whole Foods (or probably any other health food store). It's special because you don't have to use sugar to make it gel, therefore you can use honey, concentrated fruit juice, or whole cane sugar to sweeten it. I think it gels from the vitamin C water (which comes in the box with the pectin, you just have to mix it with water and put it in a jar). 
Here's my vitamin C water. It says it lasts for a few months in the refrigerator.Now for everything that I did...
First of all, put your jars and your lids into pots of water covering them and bring to a boil. You want to have them really really hot when it's time to pour the jam into them as this is what makes the jars seal. You don't have to keep them boiling the whole time, but make sure they're boiling or close to it when you're ready to pour.
Next thing to do is mash your berries all into a pot. Add the vitamin C water (I added 4tsp for 8 cups berries) and the lemon juice (1/2 cup). Stir.
Pour your sugar (I used 4 cups, but you should probably use less if you're using white sugar. Or you can use 1-2 cups of honey) and your pectin (I used 4 1/2 tsp) into a bowl and mix well.
Bring the berries to a boil, then add in the sugar/pectin mixture. Stir vigorously for 1-2 minutes until the sugar is dissolved. Return to a boil, then remove from the heat. You're now ready to fill your jars with your new jam.
Put all of your three hot pots together next to a few kitchen towels. Make sure your tongs, rags and funnel are handy. Fish out a jar, a lid, and a ring from the hot water, with tongs, shaking off as much water as you can. Pour or ladle the jam into the jar up to 1/4" from the top. Wipe the jam, if any, off the top of your jar. Put on the lid and tighten the ring. 
Flip your jar over and put it upside down on a kitchen towel. Repeat with the remaining jam/jars. My recipe with 8 cups of berries made 8 8oz. jars and one 12oz. jar with a tiny bit left over. Leave the jars upside down for 5 minutes, then flip them over. You should begin to hear them popping, which means they're sealing. If they haven't all sealed after 5-10 minutes, take the ones that haven't sealed, and boil them in your pot for 10 minutes. That should seal them.
Now you're done with your jam! It keeps for a very long time, but when you open it, it says it keeps for 3 weeks in the fridge. (I've kept it for longer and it still tasted fine). The reason I made cooked jam instead of freezer jam is because it says that freezer jam only lasts for 1 week after you open it. And this jam is absolutely delicious!
Now for the cleanup...
I had enough berries left over to make blackberry turnovers. Yum!!