Older Siblings and a New Baby
The biggest thing I notice is that people are constantly fawning over a new baby and your older one gets left out. There does need to be the idea of sharing a parent and being excited for your sibling, but for a toddler/preschooler, it is hard to understand that concept. Thus, it is important that whenever someone comments on your baby, turn to your older child and say, "When you were younger/little I used to carry you like this" or, "you used to eat like this."
This opens a dialogue up between you and your older child about what life was like when they were a baby. Telling those stories not only makes them feel useful and important, but it is also helpful for your baby to hear your voice.