I've found that a searching for ariticles through a major university library is a bit more effective than google scholar. I'm not sure how this varies from school to school, but I go to Iowa State and have had success with their website as well as Washington University in St. Louis (WUSTL) in the past. If you aren't a student at a major university you typically can still use their search engine though you won't get access to the articles. However, often if you can at least physically go to a major university library you will have full access while you're there. This was the case with WUSTL - I was an undergrad at a small school nearby with terrible library resources, so I just went into the city to use WUSTL's library for any major research projects.
If you're at a small school you probably have more access than you think through a library loan program - I've had a library at a random school somewhere copy an article out of a (relatively obscure) paper journal, send it to Iowa State, who then sent it to me at Chapman University in California where I was for the summer. I was an ISU student at the time, so this isn't an example of a small school pulling this off, but I'm pretty sure I could have done something similar when in undergrad. The specifics depend on the school you're at, but it's worth looking into.
Also, use web of science to do "cited reference searches" - i.e. searching for every article that cited a specific article or author. This can be useful to, e.g., find a newer review article or to see if anyone has addressed the error a paper made. You'll probably have to go through a large institution to use this without paying a ridiculous sum of money, but as long as you can travel to a big university library (or are a student there), this shouldn't be a problem.
I don't follow your first paragraph. Could you point to the search engines at ISU and WUStL?
I'd like to get better at doing literature searches. Luke has written a bit about this, but I still have lots of questions.
I've mostly been using Google Scholar; it seems OK, but not stellar. What other tools are useful and for what? Added: is there a good way to find papers that cite a many of a set of papers (the idea being that if I find a number of relevant papers, I want to see if there's a review which covers them)?
How do you look specifically for review papers and/or books? For example, I'm interested in cognitive skill acquisition and I've found a review paper from 1996 but I'd like to find recent review papers on the same or closely related topics and haven't had any luck. Are there specific keywords or phrase permutations that often help? Is searching just the papers that cite an older paper useful? Is searching the same journal useful?
How do you search for criticism? Lets say I've found a paper that uses a particular method or theory but I want to know whether there are significant criticisms. Are there phrases that are often associated criticism papers?
Are there any activities that are especially good for practicing literature searches?