The key to cleaning baseball cards without damaging them is to go slowly and carefully, avoid using aggressive chemicals or excessive moisture, and test any cleaning methods on less valuable cards first. Here are the steps I recommend:

Start by gathering the supplies you will need which include a microfiber cloth, cotton swabs or cotton balls, distilled water, a spray bottle, an eye dropper, and 70% isopropyl alcohol. Distilled water and isopropyl alcohol are both gentle cleaning agents that can lift dirt and grime without damaging the surface of the cards.

Inspect each card closely under bright light before cleaning to identify any problem areas. Look for creases, scratches, stains or discoloration that cleaning may not be able to fully remove. For heavily soiled cards, some damage may already be present that cleaning will not improve. Sort cards by condition to focus cleaning efforts on those in best shape.

Dampen the microfiber cloth very lightly with distilled water. Gently wipe across the surface of the card to lift any loose dirt. Avoid using too much moisture as water can damage the paper over time. Wipe in one direction being careful of edges. Check for remaining dirt – you may need to re-dampen the cloth a few times to fully clean.

For stubborn stains, use a cotton swab or ball dipped in distilled water to target clean just the stained area. Rub gently and check frequently so as not to saturate the paper. Stains that do not come out with water alone may require additional steps outlined below.

Once the card fronts appear clean using just water, move on to the backs. Clean these using the same damp microfiber cloth technique but be even more gentle as the printing can sometimes flake off the coarser cardboard material on the reverse.

After cleaning with water, use alcohol to further disinfect and sanitize each card surface. Fill a clean spray bottle with 70% isopropyl alcohol. Lightly mist the cloth then wipe across the front and back, being sure to wipe dry before moving to the next area. The alcohol will evaporate quickly without leaving streaks.

For stubborn pen or ink stains that water did not remove, try dabbing the area with a cotton swab dipped in alcohol. Rub gently and check often – ink may lighten but likely won’t fully disappear. Don’t apply so much pressure that you risk damaging the surface.

As a final step, use compressed air to blow off any loose dirt particles that may have been dislodged during cleaning. Hold cards at an angle to direct debris away. This cleans internally and helps prevent redeposit of grime.

Always store cleaned cards in protective plastic sleeves or toploaders to keep them pristine. Avoid direct sunlight and extreme heat or humidity which can cause further damage over time. With patience and care using the outlined methods, you can safely clean baseball cards and preserve their condition and value. Always test techniques on duplicates first before treating prized collectibles. With a light touch, cleaning enhances without harming card surfaces.