ROS

• Every Node you develop will be a part of a ROS Package which implies there would be so many things to consider like writing launch files, getting user inputs, including executables, generating Cmakelists, editing package XML, etc during and/or after developing program nodes.
• Try to understand what ROS is and where it fits in a Robotic system. Here are a few links here, here and here.
• Try and understand what each of these commands do: roscore, roscd, rosrun, roslaunch, rosnode, rostopic, rosbag, rosmsg etc. You could use this as reference.
• Follow this link to understand how rosnodes work.
• Follow this tutorial to understand rostopic in detail.
• Code up a simple publisher , subscriber node by following this tutorial