so here are my questions:
1. how was the yield of 60% calculated?
The values used for the caculation are not reported in the link - you need to know the mass of product obtained.
I assume you know how to calculate yield in cases where the mass of starting material and product are both known (google chemical yield calculation if this is not the case).
2. using that methods, what should I watch out for and what are some the tricks I can use to increase the yield? if you don't mind, explain why
There are many reasons why a yield might be low. In order to increase the yield of a reaction, you need to understand why it is low - i.e. find out what happened to the other 40%.
Do you have any ideas as to where the other 40% could possibly have gone?
How could you verify which of these possibilities are true? For each case, what changes do you think you could make to the procedure to increase the yield?