Can you seperate the new growths and pot them up?
If so, can you tell me when is the best time to do it?

Also, if I ever get a Keiki, when do you take it from the parent and pot it up?:)

For Dendrobiums, which is a common keikier, You do it when there are a few roots at least a few inches long AND more importantly when the cane has a bit of fatness in its bulb to support it.

In the first photo you can see a keiki in bottom middle with a few long roots. In the second photo you can see that keiki potted up.

Aww the second photo is so darling :D

Dame,

My general rule-of-thumb on dividing "colonies" of sympodial plants is to have each cluster be a minimum of 3 pseudobulbs plus a new growth. Sometimes, in a really healthy plant, you can get away with 2+1, and still get blooming when the immature growth matures. Anything smaller, and you'll likely miss a year or two.

Also, when you've divide a large plant with many growths, you'll often be left with several healthy "back bulbs" with no new growth. If they're green and plump, pot them up too, as they will often sprout new growths shortly thereafter.

As to when to pot up a keiki, again, my rule-of-thumb is when there is about 4" of total root length on it, but as is the case in all orchid things, "it depends". Sometimes they will be very tiny with plenty of roots, so I leave them be.

Another little trick that I sometimes use on phalaenopsis-spike keikies is to place a pot of growing medium next to the "mother" plant, bow down the spike and anchor it to the other pot. The keiki can then put it's roots down and grow on its own - but still with "Mom's" added support - untill it is big enough to separate.