Both are common, so it’s up to you which one you like. Till is commoner in Scotland, where it can be used like dative to in some situations, while ’til is commoner in the U.S.
The current position is that until is the more common of the two words and is generally considered to be slightly more formal, which is why it turns up more often in edited prose. It is also rather more likely to appear at the beginning of a sentence than is till. But till is perfectly good English and the choice of whether to use it or until is often decided by the rhythm of the sentence.
Matt Bellamy wrote:Until! Or the abbreviation of until, so, 'til.Ever look at a word so much that it doesn't look like a word anymore? o_O
86,728 Literary Works • 453,429 Reviews