Map control and position is very important, especially early game. It can mean the difference between getting your first few zealots before a ling rush, or barely getting your gateway by the first lings enter your base. Early recon can really prepare you for whats out there and to know where to expand. Now Positions...
I have had at least 4 games in which by mere accident, i was placed either right below or right above an apponent who could easily lock me in (Zerg and Terran) in which the case was, it was difficult to reinforce my troops or even expand, eventually having little to no map control, i lost. In a normal game, IE. ladder match or 2 vs 2, you should really focus on where your opponents are and how you can gain control over them, search for a massive choke point or a bottleneck. When expanding, take heed not to expand too far form your base, and not in a position where its difficult to defend from multiple attacks, you should never expand right next to your opponent or close to the point of being withing large strike range.
Your major concern when holding an area is how well you can control your opponent, if you can tell him where to expand (figuretivley speaking), then you have won the game. Recon is very important, keep observers near or over every expansion this way you can keep tabs on your opponent. Best thing to do is get an early idea about the map you play, and know the area's where you can gain easy control over your opponent and concentrate heavy forces in that area. Make sure that highgrounds are covered by a few dragoons, I've played many times on Showdown in which i lost map control because of seige attack from the high ground.
