I recommend you go through a tour operator that will give you a guided tour. Have you seen the recent warning out by the US Embassy in Peru? recommend www.adventure-life.com - that's who I traveled with.

I'd say that there's not a great deal to choose between the two. The driving time and distance through the Sacred Valley to take in Pisac, Chinchero and Moray would be similar whether you began in Cusco or Ollantaytambo. I would base the decision on whether you were planning to stay in the Sacred Valley as well as Cusco, this might depend on the time you had available.

Some people choose to head straight into the Sacred Valley on arrival to Cusco, it's around 1,000m lower so there's no trouble acclimatising to the altitude. They would then visit Machu Picchu, either on foot or by train, and come back to stay in Cusco. Equally, others stay in Cusco before and after their visit to Machu Picchu, and in this instance the sites you've mentioned make a lovely day's exploration from your Cusco base.

Hope that helps!

Is better to start from Cusco,
You are going to be able to visit: Pisaq, Ollantaytambo and finally Chinchero.
If you start from Ollantaytambo you are going to visit only Ollantaytambo and Chincher unless you have more time to travel an extra one hour and a half to get to Pisaq.

Cheers!

Lamas is right. Also easier to find a tour from Cusco. Only problem is that both times I've done this, the tours ended at Chincheros late in the day so lots of vendors had left.

I'd wait to book your tour until you get there, as prices tend to be lower.

You don't need a "tour". If you actually want to shop and not just do a Peruvian version of (If this is Monday, this must be Germany) then I would have your hotel call for a tourist taxi for the full day. First go to Pisac ( For the market, you will want to arrive around 9:30 am, so leave the hotel around 8:00 am, or earlier if you just want a quick peek at the top of the ruins. If you want to shop the Chinchero market, I would go there after the Pisac market, then save the Pisac ruins for the return trip back to Cusco.

Have you considered doing Ollantaytambo before or after taking the train to Machu Picchu?

Good advice from mlgb.we did exactly that trip ending up in Chinchero late afternoon which was a good time to visit as the light gave a very special quality to the place. Ollantaytambo warrants half a day at least ( we ended up staying for 3 weeks!) .

Getting your hotel to organise a taxi driver is definitely a good idea. We did it our selves and good though he was the driver, did try to overcharge us at the end of the day ( I.e. about 4 times the agreed rate). A tour would be expensibpve and probably add little in terms of experience. It is a long day though. I think we were out for around 12 hours, but it was a truly memorable day. Some photos of our time there:
http://blog.travelpod.com/travel-blog-entries/candcthai/1/1218988980/tpod.html

I'll have to respectfully disagree with mlgb and crellston re getting a taxi, although I have done that to visit some of the more remote sites in the area--had no problem with charges as the driver, after visiting the first site, recommended another and we agreed on the extra fare before departing.

I've taken tours twice and each time--particularly the first time--learned a lot, as the guide would stop along the road and point things out that you would not have known were there. Locally booked tours are not that expensive. And yes, it is a long and tiring day, no matter how you go, but well worth it.