Stand and face a patch of empty soil and press A. It will ask if you want to plant a berry, to which to select "Yes". Your bag menu will come up. Pick a berry from your berries pocket and press A. It will then be planted in the soil. Use the Wailmer Pail to water the berry if you want. It may take a day or two for the berry to grow fully
You have to wait for it to grow.
Mulch
You grow it like any other berry: You plant it, water it (if you want more than two berries to grow) and pick the berries.
You must obtain the berry first. And plant them as normal as any other berry.
You say hi to it.
http://www.psypokes.com/rs/berrystats.php
In emerald you get them in the contest hall by making them with berries.
Feed them good pokeblocks from durin berries.
The leichi berry raises the attack stat if held by a Pokemon (that what it says in heartgold but I am not sure if it's the same in emerald)
Plant them in the soil where you picked them and water them. If they dont grow then maybe your internal battery has run dry (this means clock based events like shoal cave tide and plants wont grow)
Pataya berries must be obtained from either Pokemon colosseum or Pokemon xd gale of darkness trade a Pokemon holding the berry to emerald then plant it to get more.
Lum berries are randomly given out by the berry masters wife.