There is no best way to charge a stone. It just depends on you and how you charge them.A method that is very common is leaving your stone under the moonlight or out in the sun to charge them. I'd prefer in the moonlight because somecrystals can loose their coloring whilebeing out in the sun. Here is a site that gives about 5 methods (don't forget you can always try making your own method): http://meanings.crystalsandjewelry.com/charge-crystals-and-stones/
For myself I do things a little bit different. The day before the full moon is will place mine in a bowl of salt to take out all the negative energy that could be inside of them. Then the night of the full moon is lay them outside. I do this each month so that they are always ready for what every I need. But to charge as stone with your own energy just hold It I'm your hand and think about what kind of energy you want to go into the stone. (ect. Healing, luck love are some examples) then visualize the engery going down your arm, into your hand and into the stone. So this until you feel the stone has enough energy inside of it.
Selenite breaks in water so Do Not charge it in water of any sort or anything that can get wet. To charge Selenite, place it on a dry cloth outside during the three nights of the full moon.
Citrine is self charging once its been initially charged. If it is brand new to you, though, wrap it in an oak leaf and bury it at the base of a tree for three days.
Citrine is like a crystal and for my crystals I keep them near a larger power charged crystal to keep them energized. Moonlight is a very common way to charge. I sugjesth sun for clear stones and the moon for solid. Some stones are soft so I don't use water but take sea salt and rub it on the stone before charging it with my personal power. Some keep stones in a black cloth or bag because some stones like crystals can absorb energy really easy and this keeps them from absorbing random energies. I've found obsidian needs fire to charge it due to its density. Though sometimes the sun works well too. Burying a stone in the ground is a good way to absorb death energies for healing.