A citation may be "partial", that is, it doesn't give enough information to find an article. (We already saw under "interpreting citations" how a journal abbreviation may need to be turned into the full title of a journal in order to fill an ILL request.)
Or a citation may be incorrect. Here's a study that claims that "inaccurate citations are common in biomedical literature".
Below are resources that help you find the full or correct citation--and so you can then find the full text.
You can go to ASA and look up a journal if you need details helpful to find the article. For example, if someone puts in an ILLiad request but only mentions the name of the journal and a bit of information, e.g. an author and volume number, you can use the index of volumes and years for the journal, or use its search engine, to hunt around for the article. For example, use the author's name is sufficiently unusual, use the search engine to look up the author's name to see what articles come up.
Try using the Google Scholar Advanced search screen; see lower left on this page. Putting in information from the partial citation may help lead you to the full text. Same for incorrect citations: try out permutations of elements of the citation, such as title, to see if Google Scholar brings you to the full text.
Regarding conference proceedings, try out various acronyms for the name of the conference or the society that put on the conference.
These tutorials about Google Scholar may help. See the Google Scholar module of this tutorial; it is available off the menu--scroll down to the 12th module. Also, for a video about how to use Google Scholar to start with a known article and then bring up the corresponding full text, go to this tutorial; in its menu, find the 13th module, "Have Citation, Get Article".
As this guide (VT University Libraries) suggests, you may want to check a subject specific bibliographic database to see if you can find a full citation. Same point applies to determining if a citation is incorrect. Check Lehigh's subject guides to identify databases for this purpose.
The VT guide mentions trying a "general interest database". If we take this to mean interdisciplinary, you can try:
Also:
Indexes, abstracts and provides selective full-text for a broad spectrum of magazines, journals and newspapers.
Upgraded from Academic Search Premier in 2019.
Covers 1987 - present.
Helps find current articles that cite earlier work. Covers STEM, social sciences, & arts and humanities. Has an emerging sources citation index. Useful for identifying review articles Note: Web of Science generally does not include conference proceedings in search results.