I've written a lot of things on this particular paper that I'm planning to submit to a conference; most of the things that I've written are based on my readings, attended lectures, own understanding, talks, etc. I wrote all the things on the paper by myself so I basically wrote them based on my understanding; should I cite them though?

I have my reference section but for this paper, I only put citations/references if it's something like:
(1)definitions (e.g. "Smith (1999) defined ... ")
(2)ideas from the actual inventor that needs to be named (e.g. "Smith (1982) stated ... ").
(3)data from the paper(s) (e.g. "Table 1, from Smith (1980)" )
(4)anything that needs to be "supported by someone else" (e.g. "This has been supported by Smith (1991)").

I also want to limit the actual citations/references so that I don't have to check them one-by-one to ensure that I'm citing/referring the correct things.

Other than the 4 things I mentioned above, what I've written is a mixture of my readings, attended lecturers, own understanding, talks, etc; should I cite/reference them?

I think you have to cite lectures, etc, and I also think you have to cite yourself (if it was your own paper, lecture, personal correspondence, presentation made on some public
forum). If the finding, concept or idea came from a lecture you attended that was presented by someone else-then you definitely need to cite this.

Most style guides have the appropriate citation style for all of the modes-lecture, internet site, news article, conference, personal correspondence, etc.

It's a painful process generally isn't it-especially the checking of individual citations? Probably why my second supervisor is so pedantic even with citations in very very rough drafts (!!)

You don't have to cite your own analysis that is coming forth in the paper though...as in something that you have thought, discovered, created-unless you have already published this creation previously. And you can limit having to do excessive citations somewhat, by only citing a major source-

eg As Smith (1991) noted in his work on ......or As Smith (1991) and Jackson (1980) both note-

but leaving out Green(1995), Cork (1993) and Grinspoon (1987)-who are not as major compared to Smith and/or Jackson- even though you know they said it as well.

If it is for a powerpoint or presi that you are giving with an spoken paper, I think you can get away with not citing all of the above in the pp and the speech-but (I think) they would need to be in the paper that is published as part of the conference proceedings. (Even if you didn't say all of this when delivering).

But hope I haven't misunderstood your question.

If possible, you should cite the works of invited speakers or scholars who may present in this conference.
Some professors may feel very upset because their works are very important but you simply do not cite them.

Wait, better check if this conference is reliable.
It can be folded again...

Thank you for the replies.

The talk has been cited; the speaker is a prominent member of the research community. I've also cited my own paper; I needed some data to support the paper.

The lectures; well, I heard them years ago during my undergraduate degree and the lecturers were using the textbooks to deliver the materials (I think).

If the information is something that is 'common knowledge' in the field, then that does not need to be cited. For example, if you were to write 'the heart pumps blood around the body' then that would not need a citation as it is such a well established fact. Therefore, things you learnt at undergrad may not need citing if they are ideas that have been commonly accepted into the literature. Have a look at some other examples of papers in your field to see what I mean - not every single sentence will have a citation. If you are using other people's work from conference presentations etc., then you will need to cite these. Although it is a pain checking all the citations, it will be good practice for writing up your thesis :)