Olympic,
let me add some items to Eckhards post.
On the 737, establishing final landing configuration under normal conditions is done in a well-defined sequence: Flaps 1, flaps 5, (flaps 10), GEAR DOWN flaps 15, ...flaps.....30/40 - so the point where to extend gear is coincidental with the decision to extend flaps beyond 10 (which varies due to ATC and/or descent requirements). The reason for this being a quite “annoying” aural warning if flaps are extended beyond 10 with the gear still up (airplane thinks: flaps? wanna land? then put your §$=&@!! gear down!!!).
Under exceptional and quite rare occasions the gear (without flaps) is (ab)used to increase drag and facilitate a steeper descent and/or quicker deceleration. Gear limit/extension speeds are normally higher than flap limits.