I bought a house earlier this year, in a very hot market. To the previous poster that said it's like a full time job - it really is. Booked weekends every weekend, plus emergency time off during the week. Many times a house would list on Mon/Tues and already be contingent by Thurs, before we were able to even see it. We had to be willing to drop everything to go see places, and at the same time be ok with missing good houses if the timing didn't work out.
Pre-approval is important, if you are planning on your offer being contingent on financing. Pre-approval is no guarantee, but without it, your offers won't be taken seriously. You won't have time to get pre-approval after you've decided to make an offer, you are likely to miss the window while waiting. We updated our pre-approval periodically, and if your search goes more than a few months the bank may require a new credit check.
Also be aware that in some markets, buyers are waiving inspection and other contingencies. We were not able to get an inspection before purchasing, every house we offered on had multiple offers and went with buyers willing to waive. Note that if you have waived the inspection contingency, you can often still have an inspection "for information only" but the seller is not obliged to allow it.