So I know this could be a problem for mostly guys in their teenage and early 20 years. With my ex I could hardly come so I thought this wouldn't concern me, but with my current gf there was a little issue about it and I had to do something, so I'll share what I found out by experience.
First, help from the outside. Alcohol and weed. For me alcohol can make me last longer but I need a little too much for this effect except for vodka. That worked quite well. As for the weed, it does not always make me last longer, but it definitely makes me get hard again sooner.
Second, the abdominal muscles are of great help. Flexing them may postpone the ejaculation. I found that these muscles are easiest to use, and ejaculation in all is the easiest to control in doggy style. I have no idea why, probably this just applies for me.
Third, it is important for every man not to put themselves on pressure about this. Most women enjoy sex very much even if they don't come(altough I usually insist...I just see it fair that way) And also, you can just start over.
Fourth, practice. While wanking you can practise how to last longer and there are some really good techniques on this all over the internet.
And for last, probably the easiest one. When you're about to come, just change positions, slow down, or stop for a little and start making out.
By using at least 4 out of these 5 methods(I don't always smoke weed before sex lol) I was able to add several minutes to my time, and my gf was pleased

Oh, and also, if anyone here knows anything else on this topic(I'm sure many of you do) Feel free to share it.