With the last batch of strawberries we got from the farm, I made this Strawberry jam. I had some Pomona's Universal Pectin and I used the recipe from the instruction manual to make this jam. I bought a box of this few years ago and I've made jams using this pectin before and it always worked well for me.
Some people prefer not to add pectin, but I find adding it makes the jam hold its shape better. If you prefer not to use pectin, then feel free to leave it out. Almost all fruits have some level of natural pectin in them that will help them set to make a somewhat firm to very firm jam. Here's a good article to read more on this.