Timing of identifying and closing on properties when doing a 1031 exchange

[Cassandra Brown]

I'm new to 1031 exchanges and wonder if it is wise to have identified and made offers on properties even before the closing on the property being sold (contingent on the sale) so that the closing can be quickly and I can be sure that the property is identified in the 45 day period.  I'm worried that I will identify properties and then the sale will somehow fall through and I won't meet the exchange requirements.  And, should I identify 3 properties or 200% value ? 

Thanks for any thoughts and advice.