Inspect your burners for signs of corrosion or anything blocking the row of flame holes. Burner tubes are inviting spots for spiders to lay eggs if your grill goes unused for a while. Use a wire brush and clean them by brushing back and forth over the holes, not down the length of the tube. The wire bottle brush can clean out the inside of each tube.
Clean the exterior of the grill. Soapy water is the safest cleaning solution for most gas grills. Just make a cleaning solution with water and a squirt or two of mild dishwashing soap. Wipe the exterior of the grill with the soapy water, use a rag dipped in clean water to remove the soap residue, and then dry the exterior of the grill thoroughly.