Whats the best things to do for a cold for my 4 month old baby?

TLC: Keep warm, comforted, hydrated and watch cautiously. You can gently suction secretions with a bulb syringe, cool with a moist slightly cool towel, and watch carefully. At any time there is a change in behavior, feeding habits, level of responsiveness or activity or development of a fever see a doctor asap.

Nasal saline: Keeping the nasal passages clear of mucous with generous amounts of nasal saline & suction is your best basic rx. The saline thins the mucous so it can drain out of the narrow nasal passages & more air can move through.