Robots as we all know are considered as friendly creature created by human beings as we are created by God. They are created for human being to simplify life even more basically for our daily chores with the specified sequence and even by military for the purpose of doing things which has the danger to life of human beings and thus they are developed over years to substitute human beings in all the fields.
Many of us are not that qualified to make a robot by ourselves and that why we all are anxious to know how to make a robot and even depends upon the task we want to create it for. We all have the tendencies of exploring whatever new comes in the field of science and hence a basic prototype robot can be created knowing few basic high end programming stuffs.
Robots are almost 30% programming and hence if we target one specific purpose and program it well enough then it serves our purpose and the program mostly used for this is Unix and for beginner's Lego Mindstorms series is the best and how complicated your robot might turn up to be depends upon your technical acumen.
Sure, Lego Mindstorms NXT is a toy, but it is an important toy, like a piano or a chemistry set. It's one of those items that engages an imagination and possibly opens doors to new interests. Since our future is surely to be shared with robots--it's already started happening, just look at Roomba--those robots will need, at least initially, humans to program and maintain them. Those people, years from now, will likely remember their experiences with Lego Mindstorms.
While learning how to make a robot we should always keep in mind that fewer the moving parts be of the robot better it is for the beginner's as for start up we might just want it to move from here and there or hold something and sort of stuff. We should link if-then statement well and it should be taken care of that battery is never less then 50% and if so happens it should be re charged.
Thus we now understand that knowing how to make robot can never be known as there is no limit to what can be achieved with the knowledge of science and development of robots can never end.