The pragmatic pointer mentioned are great for planning ahead, but overall, you should be adaptable. Problems can arise unexpectedly, and it’s possible you’ll be delayed by interruptions or a lengthy introduction. Do your best to not get flustered, to handle yourself with grace, and to end your talk on time. Make a note of places in your talk where you can go into greater depth if you’re running ahead of schedule or places (particularly toward the end) where you can skim over the details more quickly if you’re behind schedule.