offhand and without going into too much detail:
- think about how and in what situation you will be using it: e.g. will you take taxis often (then you need an easy, one-hand fold-able one), will you walk up and down steps rather often (then it should not be too heavy), will u go shopping (then you need the ability to store goods underneath or hang a bag on it without it dropping over from the weight), etc.
- up to what age you plan to use it? many simple models can only be used when babies are small and then you would need to buy a larger one (which really also depends on the size of your baby). for that reason alone i would never buy my first stroller before the baby is born anymore.
- are you tall, or smaller build yourself? i had tall dutch friends and their model could not adjust the handle. big pain if you need to bend down to push it comfortably
- you can buy online or through classified ads but i would strongly suggest to test-push the model you plan to buy in a store or somewhere. it's like a car, you test-drive before you buy
- some things which get promoted but personally i find them useless: the ability to reverse the seat facing you or facing out. only very small babies like facing you and that time passes too quick to even notice the use. rain covers: who is outside when it rains? i used ours like once only - ever. stroller design: some people like to make fashion statements with their strollers; completely useless in my mind since the only thing we discuss about ever with regards to strollers is functionality - at least among men
we have a pegperego p3 which is rather too big but fits in taxis, our apartment, etc. i like the fact that we can use it for our small baby/kid to probably up to 3 years old (since he is small). it doesnt topple over, regardless of how much weight you put on it. has plenty of storage (less need for carrying shopping bags), it's suncover works like an additional bag when folded. on the downside and apart from size, it has two handles rather than one bar which makes it more difficult to fold (tough to impossible if you travel alone with your kid and the kid is not in a baby bjoern/ergo).
advantages ourweight detriments for us with this model. i had friends who bought what looked like a better model but had to buy a new, bigger one since their big-size baby outgrew their fancy model within 6 months.
most important advice though: even it's your first buy, don't buy original. buy a cheap one second-hand (300-800 HKD) and test it out. if it works, great. if it doesn't work, you have not spent too much money and by then know exactly what you need and whether it's worth to spend top $$$ to buy a new one
my 5 cents