How do you put a sleepy baby to sleep?

Mummy wrote this in desperation. Anyone out there able to help?

"I have been having problems putting Hayley to sleep every night in the last couple of days. When she was much younger, it wasn't much of a problem. We'll put her in the cot, pat her buttock for a while and she will eventually go to sleep.

As she gets older and wiser, it became harder. Since she knew how to crawl and stand, the moment we put her in the cot she will start climbing and standing in the cot and playing by herself. After letting her play for about 10 mins, we will hold her down (she sleeps facing down) and pat her buttock. She will resist and cry (without tears most of the time) for about 10 mins and then eventually fall asleep.

Now, the moment we put her in the cot, she will cry. Most of the time it's fake cry and if we let her continue, it will become real tears. When we hold her down to 'force' her to sleep, she will resist even more and cry even louder and sometimes she even throw up. I tried various methods of putting her to sleep from letting her head rest on my shoulders while carrying her, putting her close to my body whle continuing to pat her buttock but nothing seems to work. She will still resist and cry although you can tell she's tired.

What else can I do? Friends suggested that I need to train her to sleep by letting her cry on her own. When she realised after a few days that no one will come to the rescue she will know its bed time. Do I really have to do this? It sound so cruel to me."

I hope mummy won't leave me alone to cry to sleep every night.. sigh...pray hard...