Running races - question about pacing

I believe conventional method is to increase your pace in each km, so start of slow and keep building. I dont race much so i cant really say if it works or not. Id say your best bet is to slowly increase your average speed and still try to kill it at the end but im far from a pro, barely a novice

Running more distance, regardless of speed, will make you faster. However, that doesn't mean there aren't things you can do while racing to help you run more efficiently.

Read this today from Coach Jenny Hadfield and thought it was super helpful (for a 5K at least):

"Take the four parts of the race and color them in with Yellow (Mile One), Orange (Mile Two), Red (Mile Three) and Fire (yes this is a color and it aptly represents the final .1 mile kick). Now, run by color – rather than your watch! The body doesn't know pace. It knows effort. Run by your breath and keep it easy for the Yellow Zone (Happy) or mile 1 – you should be able to talk. If you can't, slow down. For mile two, take it to the Orange Zone – or at an effort level a little harder than Yellow, and an effort where you can hear your breath, but you're not gasping for air. As you run past mile two, pick it up slightly and head for mile three. This is what you've paid for, and the time to go fishing. Cast out your invisible hook and catch a runner ahead of you (one that went out too quickly and is suffering the consequences) and reel them in (nicely!). There is nothing more empowering than to pass people in the final stages of a race. When you hit mile 3, run tall, keep your effort, and prepare for your finish line dance. When you have the patience to pace yourself from within and from the start, you will have the strength to finish like a super hero."

You might want to focus on the two goals independently. Meaning, if you are wanting to improve distance it might be better to focus on distance before focusing on the overall pace combined with your distance. Improving your 5k time by itself will translate to a better half marathon time, even if you do not sustain your 5k pace for 13.1 miles. There are a ton of articles about Fartlek and speed training as part of half marathon training. Also people find a lot of pace benefits from occasionally splitting their long runs, i.e. doing 3 miles in the morning and 3 miles in the evening.

The number one thing that has improved my overall pace is strength training. I went from 13:08 min/mile 10k PR to a 12:21 min/mile 10k PR after adding in strength/cross training.