Ann4New I'd second what Like says - it's all about the naps. Do whatever you can to get them to sleep after an hour or so (white noise, sling, pram, bouncer, co-sleeping, car ride).
DD (now 3 years old) never napped. I (stupidly) thought that babies just dropped off when they were tired. Looking back at her first few months, I feel like she cried all the time. With hindsight, she was exhausted. We tried lots of things to get her to sleep, to no avail!
DS (8 weeks) seems a lot more easy-going, but I think that's because he sleeps well during the day. He can only go for an hour of being awake before he needs sleep. I glance at my watch each time he wakes and then I know when he'll need a nap. As a result I have a happy, smiley boy who is much 'easier' than DD was. This may also be down to his personality or the fact I'm more relaxed.
I must say, though, that (after the first three months) DD has been a real joy. She is the happiest, friendliest and most confident child I know. She is always singing, has lots of friends at nursery and adores her new brother. I know from experience how hard it is when your baby seems unhappy, but it doesn't last.