It's a long day, often 10-12 hours without a break. But if you love kids it's rewarding :)
You need to be super organised, patient, have lots of common sense, be sensible, be able to have fun and play with the kids, have good imagination, be reliable, punctual and responsible.
As others said, not such security, no 'promotions', often no bonus, sometimes cannot choose your holiday dates, your contract can be terminated at any time.
You really can only do it if you're passionate about children - otherwise you'll hate it. Personally, I love it! I get to play, laugh, have fun, go on day trips, cook, bake, paint all day :) but when the tantrums strike, my god it's hard work!
I started with no qualifications and just babysitting experience and have worked up from there. You could get a job as a mothers help first.