In the current market, where in most places there is no shortage of supply, price is key.
Sellers of apartments in complexes should start by Googling "buy apartment in [name of complex]". Their apartment at the very least should be the same price or lower than similar apartments in the results of this search. However, bear in mind that many of the results displayed will be over-priced apartments that may have been on the market for years, so a further discount will probably be necessary.
The "best apartment on the complex" will always have a chance of selling at an inflated price, because there is always that buyer looking only at penthouses etc. However many owners mistakenly believe that their apartment is "the best on the complex" when the reality is that it clearly is not.
Seller's need to objectively put themselves into the buyers shoes and ask "what would I pay for that apartment".
Another consideration is whether to rent out the apartment in the meantime to at least get some income. In my experience rented apartments are less accessible, less presentable and hence less saleable. If you want to sell, especially now that the market is moving again, keep it unoccupied if at all possible.