Berry farming is a task best left until after you beat the Elite Four, or at least after you acquire the HM Fly. Berry farming is hard work and you need to be able to get to all of your berry patches several times a day. I suggest you just clear cut the berries in the early part of the game and keep one on hand (at least) to use when you start your farming career.
The first item you will need to begin your farming career is the Sprayduck. It is a watering can shaped like a Psyduck. With this item you can water the berry patches to avoid having them dry out. You can acquire this item from the flower shop in Floaroma Town. This same shop will also trade you stuff for your berries. Once you have the Sprayduck you can begin your farming career.
Depending on the climate in which the berry patch is located you may need to water the patch more (or less) often than other patches. The Sprayduck is what allows you to water those patches.
Each patch goes through three stages of wetness:
Dark brown - Fresh soil ready for planting
Medium brown - Still good soil but it is starting to dry out
Light brown - Dry soil, get that plant some water!
I have found, through extensive research, that you will get the biggest berry harvest if you can keep your berry patches dark brown. I have managed to pull 15 berries off of a single bush by keeping the soil dark brown through the entire growing proccess. This is hard to do for berries that 96 hours to mature.
Berry Watering Tip: Soil dries out faster in the daytime than at night. Always water your patches right before you go to bed at night and every few hours during the day.
There are some places in the world where you can plant four berries side-by-side. These are the best patches but they are not always in the best places. I have found that if a patch is too far out of the way I just leave it empty. If I’m planting 30 berries and watering them every few hours I can burn 20 minutes just getting all of the easy to reach patches!
And for location any patch will do. [ dark soil works best ]
Sorry got to go, I'll answer your other questions in da moring [ well the USA morning ]