Ive made 8 or so different recipes and here's what Ive found:
Using a proven recipe and following the measurements exaclty is key
With any jam/jelly recipe, use the the called for pectin type (some use liquid, some use powder)
Don't double recipes, make two batches if you have to.
Nothing worse than a batch not setting up ( usually attributed to not following the above)
This is my fave recipe
Ingredients
1/3 cup finely sliced dried apricots
3/4 cup white vinegar
1/4 cup finely chopped red onion
1/2 cup finely chopped hot peppers (I used inferno peppers)
3 cups granulated sugar
2 tbsp powder pectin
Instructions
In a large deep saucepan, combine apricots and vinegar. Cover and let stand at room temperature for at least 4 hours or overnight.
Add red onion and hot peppers to apricots. Stir in pectin. Over high heat, stirring constantly, bring to a full rolling boil that cannot be stirred down. Stir in sugar. Boil hard, stirring constantly, for 1 minute. Remove from heat and quickly skim off foam.
Either can (process for 10 minutes) or refrigerate for up to 1 month.