@Travis Hewlett. Hard to top @Brian Burke and @Ben Leybovich! I have not had the pleasure of meeting Ben, but have with Brian, and his thoughts are always beneficial.
I have been in real estate for 25 years in MF condo, MF rental, SF, Townhomes, Notes, Retail and Self Storage. What I have learned is no market stays hot forever. I see many who approach it like their market will never have a down turn, and for me that is the most dangerous position. I will try to answer a few of your questions. Please keep in mind there were many factors which caused the Crash in 08-09. The biggest factor was the underlying assumption on the market combined with the lending structures propping it up. It was not sustainable at any level. That being said, I don't see the same extremes in the market place today, but there are some commonalities in specific market places.
What I learned from the crash - When everyone is investing in one market, sell don't buy. In 2008, I saw doctors, lawyers, even carpenters I used to hire buying property for tear downs far above market price. They were all buying on speculation and growth. They did not respect the fundamentals of the market. I stopped buying and sold. I was even criticized for selling "low" as I was wanting out of the market. I am thankful that I was able to see the signs. One was many "experts" were forecasting the downturn.
The other thing I learned was, entities were desperate to place money. The majority went to one market - apartments. It was the only commercial real estate any lender would loan. As a result, the apartment market took off. The other strong growth was senior care (similar to MF with a higher entry barrier). Personally, I see many of the same conditions in the market place - properties being bought at historically low cap rates, growth based upon speculation, and now inventory. The markets are beginning to outpace the demographics.
The last point I learned was those with cash - crushed it post crash. They could buy at the right prices points. Real estate can with stand a market correction, if it is positioned correctly with respect to debt. The reason the SF market crashed was it was over leveraged. The leverage was so high because of speculation and trying to create ridiculous rate of returns to compete against the stock market.
How long for the market to bottom out - I agree 3 years to get to the very bottom. Market timing is very hard. Most of the losses however were realized in the first 18 months.
Indicators in markets that helped investors know they would recover - each product type has its own indicators. SF very different from Self Storage, etc. That being said, jobs and education typically drive the market. People tend to go where there are jobs, and want their kids to go to good schools. The better the jobs and schools typically the better markets - not just for SF, but the other markets as well. That beings said, real estate taxes, state taxes, climate have all impacted the market places. We have had friends leave our market for similar jobs in lower tax states and communities. That is partially the reason TX and NC are growing.
How to prepare for the crash - Buy right and don't over leverage the properties. Make sure the purchase reasons are based upon the fundamentals not speculation. We study demographics and market conditions before we consider purchasing a property. If those factors are not solid existing conditions, we don't move forward.