Before you start, please read these points carefully:
First of all, you must have a recent version ($3.0.0$ or higher) of R installed. You can download the latest version of R from this page: http://cran.r-project.org/.
The lavaan package is not finished yet. But it is already very useful for most users, or so we hope. However, some important features that are currently NOT available in lavaan are:
full support for hierarchical/multilevel datasets (multilevel cfa, multilevel sem); however version 0.6-1 supports two-level cfa/sem with random intercepts only, for continuous complete data
full support for sampling (and other) weights (0.6-1 has sampling weights, but only for complete continuous and non-clustered data)
support for discrete latent variables (mixture models, latent classes)
Bayesian estimation (but see the blavaan package)
We hope to add these features to lavaan in the near future (but please do not ask when).
We consider the current version as beta software. This does NOT mean that you can not trust the results. We believe the results are accurate. It does mean that things may change when new versions come out. For example, we may change the name of the arguments in function calls. And we change the internals of the source code constantly. However, the model syntax is fairly mature and has been stable for a while.
We do not expect you to be an expert in R. In fact, the lavaan package is designed to be used by users that would normally never use R. Nevertheless, it may help to familiarize yourself a bit with R, just to be comfortable with it. Perhaps the most important skill that you may need to learn is how to import your own datasets (perhaps in an SPSS format) into R. There are many tutorials on the web to teach you just that. Once you have your data in R, you can start specifying your model. We have tried very hard to make it as easy as possible for users to fit their models. Of course, if you have suggestions on how we can improve things, please let us know.
This document is written for first-time users of the lavaan package. It is not a reference manual, nor does it contain technical material on how things are done in the lavaan package. These documents are currently under preparation.
The lavaan package is free open-source software. This means (among other things) that there is no warranty whatsoever.
If you need help, you can ask questions in the lavaan discussion group. Go to https://groups.google.com/d/forum/lavaan/ and join the group. Once you have joined the group, you can email your questions to email@example.com. If you think you have found a bug, or if you have a suggestion for improvement, you can either email me directly (to alert me), post it to the discussion group (to discuss it), or open an issue on github (see https://github.com/yrosseel/lavaan/issues). The latter is useful once we have agreed it is a bug, and it should be fixed. If you report a bug, it is always very useful to provide a reproducible example (a short R script and some data).