Ah yes, the Viridian Forest. Early game in general is probably one of the few places where I find grinding to be a necessity. Catching so many new pokemon, and at such low levels, sort of sets you up for failure if you're not careful. At least, as long as you're trying to level evenly.For me, Grinding tends to be to even out levels and I usually aim for a point where I can comfortably take on the next boss.
Case in point: In Fire Red, I tend to grind everything to Level 8 before Viridian Forest, then just before Brock, I bump everything up to Level 11.
X and Y have such an easy time grinding though. Battle Chateau with the Writ that makes people cycle in every minute, and the Furisode Girls all use Audinos. Me and my friend were able to keep 20+ Pokemon on level just to keep each other guessing (We were battling after every Gym).