Step 1: Jar sterilization I wash my jars then place them in a boiling pot of water for 10 minutes. I boil the lids but not the rings. The rings should not come in contact with your jelly. In fact if you seal your jelly correctly you won't even need your rings (although I still use them). Once they are all sterilized I place them on a clean towel off to the side.
Step 2: Making the Jelly In a large pot (I highly recommend a Paul Deen no stick pot for this) place washed berries into a pot and mash them. Bring them to a boil and add sugar. Ensure to stir frequently to prevent burning.
Step 3: Jarring Add mixture to sterilized jars. Ensure rims are kept clean to prevent mold. I use a jarring funnel to help prevent a mess and having to wipe rims. Place on lids (always use new lids) and put on the ring. Ring should be loosely tightened, no need to use heroics to seal. In fact if you tighten too much they may not seal properly. In a good seal the lid will suction onto the jar and you can remove the ring entirely if you want.
Step 4: Sealing To ensure a good seal place lidded and filled jars into a pot of boiling water to boil. Time varies based on your altitude, there is a good little chart on page 6 of this PDF to determine your boil time.
If after you boil your jelly to seal them, they become runny don't worry. Give them time to cool off and they will firm up.
If the lids don't pop in the boiling process. The lids may seel & pop a few hours after the boil process.
What you should worry about. If the lid does not pop the next day. This jar did not seal correctly. You can try again to boil and seal, or place it in the fridge to be eaten first.
How do you know your jar is sealed? You know your jar is sealed when the center can no longer be pushing in and out. When it is sealed properly the lid is firm on the top and sucked into the jar ever so slightly. You should be able to remove the ring and the lid will not come off without some prying.
Always refrigerate your jam after the seal has been broken.