Freezing the lane while zoning the enemy is usually preferable because you're cutting them off, but you shouldn't be afraid to push bot lane. Bot lane is not about freezing the wave like top lane is.
The side that gets shoved under tower with no successful counter pressure generally loses, but there are a few exceptions. Truthfully ADC matchups bot lane are unforgiving, so outside factors are what really matters.
Pushing the lane is fine unless the enemy ADC can safely farm under tower and you don't have vision. A LOT of ADCs forget that they have a warding trinket, and it is absolutely crucial that they ward with the support because they don't get wards until around the 8 minute mark.
The next step in the decision process depends on who the enemy jungler is and what side of the map you're on. For example, you won't want to push against a Hecarim unless you've warded deep because he can get to you guys before you have time to back up. In some cases you and your ADC will need to buy control wards for champions like Evelynn (In general if you're pushing, the support should try to buy one). In other cases you'll need to ward in specific areas like if you're on blue side against a Kayn, ward behind the wall instead of just in the river bush because that's usually how they gank.
As long as the support pays attention to the mini-map and looks at what is going on around, and the ADC listens to their pings (easier said than done), then they shouldn't have a huge issue with ganks. The only exception is the dreaded 4 man dive, and if you see your midlaner performing poorly, then you save everything for that moment because it will come and you better believe the midlaner that lost won't call missings or push mid tower. Its good to have a contingency plan in place for these types of matches because counter pressure bot lane isn't always a guarantee either.
[sg-lulu]
Experience is what matters. There's no hard and fast rules when it comes to this subject because every situation is different.