In addition to these directions for how to use this tune index site, see also here for some basic information about traditional folk music.

To find a tune you can either identify its category (Tune Categories) or search for it.  When you look for it by category, you will see a list of the first few measures of each part (typically there are two parts, but not always).  If you want to print a page of these incipits, setting your printer to "landscape" works best.
 
You can search for words which have special characters (non-English) either directly or as though the accent marks were removed.  For example, you can search for "Rättvik" by entering "Rättvik" or "Rattvik".  Except for file names the proper spelling is always used, but almost everywhere the unaccented "spelling" is also available for searching.
 
Each tune is numbered with a 4-digit arbitrary identifier, starting at 1001.  If you know a tune's number, putting it in the search box is the easiest way to find it.

Almost 50% of the tunes have an icon indicating that an Adobe Acrobat PDF file of the whole tune can be viewed, downloaded, or printed -- just click on the icon.  Of course, it would be ideal for every tune to have a PDF version, but it may take a very long time for that to happen -- like everyone else, I have binders full of multi-generation photocopies.  Identifying the tunes is a useful first step, and more transcriptions of complete tunes will follow.  If you would like to see a PDF for a particular tune right away, please contact me.

The tunes that have a PDF icon may also have an ABC icon indicating that an ABC file is available -- just click on the icon.  These tunes may also have links to FolkWiki, an archive of ABC files for Scandinavian tunes.  Go there for more variants and information.
 
Tunes that originate from workshops since the site was first published in 2005 may also have an audio icon indicating that an MP3 of the tune can be opened or downloaded -- just click on the icon.  Sometimes there is a slow version as well.  These recordings are produced with the permission of the instructor(s) and are limited to non-commercial use.

Transcriptions of tunes come from many hands, including mine, and may contain errors.  Sometimes the tune's name or context is not known to the transcriber.  Individual performers play the same tune differently (often in the same performance), the tune itself exists in variants, and ornamentation is individualistic, difficult to notate, and hard to read.  It is best to think of these tune transcriptions as skeletons of the melody with much of the performance practice omitted -- there is no substitute for listening to actual performances.  (See this excellent article by Matt Fichtenbaum on the limits of musical transcriptions.)

Note: Scordatura tunes (non-standard GDAE tuning for the violin) are generally notated as fingered not as sounded, unless otherwise mentioned.  See Special Tunings for more information.

Look for the maps link for tune categories that are associated with a particular region - you will find it on the top right corner of the page, when relevant.