Without getting into every detail after installing ABAP Development Tools, which requires SAP GUI installed, with existing logon information to the various systems, we would like to explian you some features of ABAP in Eclipse, mainly for developers not using eclipse for development in other languages previously.
First of all, after installing and starting eclipse choosing a workspace folder, you can create a new ABAP Project under: File - New - Project. Here type in ABAP to find the ABAP Project. This will open a wizard, where you can select your system configured in SAP Logon. If you get some exception, check out this guide to configure the Backend System. There is no exception, for the first you need to wait a bit (backend compiles, workspace in eclipse gets indexed).
After you want to start working on ABAP Objects, that is great, but how-to do that? You want to execute common tasks, like navigate to a method of a class, go to the definition from the implementation. Editor is source code based, no form-based edit possibility exists (except wizards or quick-fixes), and there is no display mode. It is time to learn how ABAP syntax looks like of a class ;). Development of ADT considered the same Keyboard shortcuts in the debugger as in ABAP.
Tip 1 - Help Content (adopt)
Choose Help - Help Contents in the Menu, and see the magical info source, which helps you to get familiar with ABAP Development Tools. You find here tutorials, feeded from help.sap.com also, which is great. If you are looking for the ABAP reference, press F1 in a source loaded from a particular system, to have the right Help Content considering the basis version of the backend system from where your source object originates.
Tip 2 - Focus more easy when analyzing and reading the source code (configure)
This is not marketing, but frankly, Eclipse beats ABAP Editor in SE80. The highlighting of the same variable has different colors when read or write access is shown.Beside this, find customizable coloring, to make even difference between the ABAP keywords. They are not just blue anymore, wow. I like it.
Of course, you have more gain over your environment. There are lot more editor customizing features overall and dedicated for ABAP and CDS. I plan to release a custom Dark theme for ABAP and CDS soon. Once you learn it, you are more effective with ADT, than with SE80 before.
Homework: What is an ADT Link ?
Tip 3 - TAB settings, to match the ABAP Editor in SE80 (configure)
TIP 4 - Create/Open/Execute ABAP Repository Objects (develop)
In the good old SAP GUI environment, you created Objects in couple of different transactions. This ends with ADT, like you open or execute any object using the toolbar, you can create any object using a wizard. If there is no equivalent editor for your object type, then SAP GUI opens. You need to open the ABAP perspective in advance. Top-right corner, next to the bug, or Window - Perspective - Open Perspective.
Push the folder button with the SAP icon. Start typing...
In higher backend releases you can also prefix your criteria, to have results faster, and restrict your search with "CLAS:" or "MSAG" for example)
Pretty much the same, but click the play button with the SAP icon instead
Creating Objects (Any)
Push first button, type in "ABAP" in the wizard, choose ABAP Repository Object.
You can create other objects dependent on the context in the Project Explorer with right click.
TIP 5 - Enhancements
Don't hit me when talking about Enhancement framework, in ABAP in Eclipse :O, there is no such. But of course SAP GUI opens in a new editor tab within eclipse, when you want to see an enhancement and navigate. This is valid for all ABAP Objects, which is not supported by ADT at the moment. Examine the Window - Preferences menu yourself and find, when you want to let eclipse open a separate SAP GUI window instead of a new tab, reusing your SAP GUI installation.