どうやら

どうやら means "apparently", "it looks like": the speaker has put the clues together and reached a conclusion. It goes at the start of the sentence, and the sentence ends in a word of conjecture – ようだ, らしい, みたいだ – which carries the "seems".

Leave the ending off and the sentence sounds unfinished: ×どうやら彼は来ない. どうやら works in speech and writing alike.

どうやら or どうも

どうも with the same endings also means "it seems", but it leans on a vague feeling that something is off. どうやら leans on evidence, and the conclusion is firmer.

"Somehow", "just about"

With a plain past verb and no ending of conjecture, どうやら means the same as どうにか: something worked out, but only just. This use is less common.