Well if you were in that game with them, you should be able to look at your autorecord folder to see them, right?
Nearly all of the ICO regulars have a pretty good sense of the first 15 minutes, it isn't all that complicated, especially if you've played a good number of games and understand the game mechanics.
Take your roid, build a moderate fleet of the proper ships to fight off enemy caps and their initial fleet, if you're Vasari get all the neutrals you can, maybe get a civic lab to get Terran pop research, maybe build another cap to provide strike-craft and bombing support... once you have a moderate fleet research +hull and maybe armor if you're TEC, etc. The first 15 minutes in a 5v5 are not very special if you're on the flank. I think. You and most everyone else probably already knows this sort of stuff. Looking at replays is excellent for teaching new-ish players how to do this sort of thing, and for how to fleet, and how to micro - but what really differentiates the top-tier players (like Howthe?) from the others is their macro skills, I think. And those great macro skills usually become apparent somewhat later in the game, after the pro has mostly neutralized their near opponent on the flank, once the pro is expanding (sometimes in multiple directions) while managing fronts on many sides. This sort of skill especially shines if the pro spawns in the eco slot.
While looking at replays can help a lot with learning to fleet and micro, a problem is that it's somewhat difficult to look at a replay of a skilled player and then conclusively determine a good macro strategy, let alone replicate it.
If there's some specific area you know you can do better in it's easier, rather than just "how to be pro?".