Mentoring them. Nothing is better than an experienced engineer going to the site with them and explaining this and that. They need to have the geo report available as well. A thorough understanding of soil mechanics is also a plus.

Agree with jmcc3265. Mentoring, and having resources (ie competent and open senior engineers that they can discuss issues with) is the single most important thing. The best thing you can do is try to instill an attitude in them where if they do not know, they will call you (or whoever the responsible senior is), give an honest explanation of what is going on in the field, and ask for your advice. Unless of course you want a bunch of orangatangs running around in the field reducing the compaction spec to 90% from 98% and not telling anyone until the structure is built.

You get to have college educated field personnel?

mentoring... but some side reading....Geotechnical Testing, Observation, and Documentation by tim davis..... another good one Soils, Earthwork, and Foundations by Meyer et al
fyi....both are study materials for icc soils special inspector cert

Thank you, all. I 100% agree that there is nothing better than learning from an experienced mentor.

Good answers. However, for some reason some inspectors feel they are "in charge" and feel asking for help is not really needed as long as they feel confident with what they do. I've had a few of these kind of engineers. In a couple of cases they even disregarded what I told them about the situation and what to do. Needless to say some drastic action on my part straightened it out. I suspect it probably boils down to making sure you and the inspector have a good communication arrangement from the beginning.

Of course all new field personnel and even experienced personnel need mentoring and improving their learning and experience. Oldestguy has a point - which is why the office lead geotechnical engineer should also go to the field from time to time to see what his staff is doing. But the question was what training help could be had.

You might check out the following:
http://www.idot.illinois.gov/assets/uploads/files/...
https://next.lexingtonky.gov/sites/default/files/2...
https://www.dot.ny.gov/divisions/engineering/techn...
http://wwwsp.dotd.la.gov/Inside_LaDOTD/Divisions/E...

In other words, many state departments of transportation have such manuals. I've seen a few good ones from Florida on MSE wall inspection and other topics.

Besides the technical stuff, I would try to keep them motivated and enthusiastic to work in the geotechnical field. I have seen young engineers that think that everything is in the book, and do not realize that they need to go to site and observe things and talk/ask question to senior geotechnical engineers. IMHO, I feel that motivation is the key to make people grow up.