If you are still looking, there is a rough guide to the pronunciation of different letter combinations here. If you prefer examples and rules, I have compiled the following, expanding on the comments made by epac-mcl and ThomasTQ. Please be aware I am not a native speaker or a qualified linguist. Corrections are welcome.
v = [v] • at start of a word and before vowels (i.e. vred 'angry', vejr 'weather', udvandring 'emmigration'); • between vowels (skrevet 'written', lave 'make'). Exceptions: some commons words below. • after most consonants, especially common are h, k, s (hvem 'who', kvinden woman, svare 'answer'). Exception: l, see below.
v = [w] (sometimes also [u], sounds more or less the same to us) • before most consonants (common ones are d, n, l, s; more rarely r, [note vred above]) or at end of word (i.e. savne 'miss', brev 'letter(s)'). This does not seem to apply if v is also at the beginning of the syllable/word. Exceptions below.
v = silent • after l (i.e. selv 'self'. Rare exceptions ulv 'wolf', selve inflected form of selv); • in rare, but extremely common words such as blive, have, including past tense havde which is pronounced the same a hade, 'hate'.
So, a simplified rule might be: v is [v] at start of a word, after consonants & between vowels but [w] before most consonants; v is silent after 'l' and in some common exceptions.
If you are still confused, it might be worth looking up each new word in a good online dictionary with recordings, and remembering this word. I recommend this one, even if the entries are in Danish, most words will have a sound file you can click on as well as a phonetic transcription of the word which you can use to compare different forms.
Hope that helps!
Not really (completely) correct, I'd say, sorry. For instance, in your "skrevet" and "lave" I only hear a [w] sound, never a real [v].
Furthermore, ordnet.dk seems to be quite unreliable, too. For example, "have" (garden) is said to have a [v] sound, whilst I only ever hear it pronounced with an unsyllabic u sound, or let's write it [w].
Which Danish word were you thinking of? I can't think of any which starts with a "v" and pronounced like a "w". On the other hand, there are absolutely very few words in Danish which begin with a "w", and these are mainly imported words from another language. You will hear these words pronounced with both "v" and "w".
No words starting with "v" is pronunced as a "w". On the other hand, many words borrowed from English starting with "w" is pronounced with a "v" sound, for instance weekend, web, and wok. But just as many start with the original "w" sound, like whiteboard or widescreen. There are no general rules, just ask a Dane.