Though it’s generally not something that we’d suggest doing, there are instances where it’s not a bad idea to apply a little EQ during the recording stage of a project. High-pass or low-pass filters can be used to reduce or eliminate bleed from other instruments. For example, use of a low-pass filter is effective in reducing the amount of cymbal sound picked up by the kick drum mic (start around 7 kHz and adjust from there). On the flipside, a high-pass filter can be used to lessen the amount of kick drum and tom bleed picked up by the overheads (start with a cut at around 200 Hz).
Many microphones, interfaces, and preamps are pre-equipped to cut low frequencies. The most common use of these low-cut switches is to lessen the “rumble” that occurs from people walking through the room, passing traffic, etc. The low-cut switch can be used to battle such issues as proximity effect as well. If your mic, pre, or interface isn’t equipped with a low-cut switch, an EQ cut in the range of 100-200 Hz can help alleviate proximity effect while still allowing for close miking.