It's very difficult to give general advice here : it might be easier to adress a specific openign scheme.
However, in these kind of setup, it's generally a good ida to take strong control of central squares that your opponent has neglected - for example : 1.d4 d5 2.e3 Nf6 3.f4 Bf5 (control of e4)
My friend and fellow chess lover is a strong all-around player, but recently - in the last four or five games - I've noticed that he has been playing unconventional openings that involve heavy pawn development. Typically, his first move (as white) is d4, followed by at least two, and sometimes three, pawn advancements (e.g., something like f4 and then e3) preceding a move like Nf3 or Nc3. In response, I typically counter with normal development of knights and bishops, in attempt to gain standard positional advantages. However, in many games in which I defend against such openings, the strong pawn movements forward can be difficult to develop against, especially since I usually work to open in traditional ways that assume minimal pawn advancements. What sort of strategy is most effective against an opposing side that is attempting to gain horizontal dominance across the center of the board? Is it a symmetrical strategy that counters with similar pawn advancements? Or is it best to develop minor pieces in a traditional style - following classical principles of attacking advantages? Are traditional defences equally as effective against this sort of opening, or are there other principles that must be employed in order to face this style?