The Globus Toolkit includes some very useful documents. The ones most related to this document are:
Java User's Guide: $GLOBUS_LOCATION/docs/users_guide.html
Java Programmer's Guide: $GLOBUS_LOCATION/docs/java_programmers_guide.html
Programmer's API: $GLOBUS_LOCATION/docs/api/index.html
Substitute $GLOBUS_LOCATION for the root of your GT3 installation. A team at IBM lead by Luis Ferreira has written a thorough Redpaper titled GT3 Quick Start which explains the GT3 installation process in detail.
GT3 users have also contributed installation and programming guides:
From Zero to GT3. Written by Ian Stokes-Rees.
Grid Install for Windows 2000 Platform. Written by Michael Schneider.
Once you've become a Grid Services expert, you might have to occasionally take a look at the OGSI specification, available at the OGSI Working Group page.