I have a 21 month age gap - DS2 is now 5 months. There are some fantastic tips by PPs.

My tip (which I'm still remembering to do) is always to take the baby carrier out with you, even if you take the double pram (if you have one). Often I think, I'm just popping in, I'll just put them in the double stroller. But invariably, one or the other wants to get out and I still carry by toddler on my back, when he's crankypants. So always good to have the carrier, because juggling a baby and a toddler without one is really hard!

Also, put the baby stuff out early so your older child can get used to it and over the excitement of a "new toy" (i.e. bassinet on wheels AKA giant car!). Or you can teach them not to touch it.