If you're referring to the Crusades to the Middle East (the Baltic ones wer eobviously rather different), the scouting and skirmishing duties were usually left to the Turcopoles who were rather better suited to it in the context given that they could more or less take on the Turks on their own terms.

Medieval campaigns, however, were overall mostly affairs of maneuver, skirmishing, siege and ravaging the enemy lands, with decisive field battles being rare - this both East and West. Obviously mounted forces were of prime importance due to their sheer mobility (and hitting power particularly in small-unit encounters), and while a lot of it was on the shoulders of assorted lighter cavalry and irregulars the chivalric heavies and their colleagues from other cultures were doubtless heavily involved, both as a sort of heavy reserve and as the "officer class" of the armies.

Nomads, naturally, could just sends some of their tribal cavalry before the main host to do reconnaissance and try to keep enemy scouts and harassers at an arm's lenght.