{ I have posted this post from @ppppking04 here as a Beginners Guide to Forum Posting
There are millions of pages on the internet about all of these, just search for it. Here's a quick(!) guide for the uninitiated:

Step1. Think about what exactly what you want to do (say a basic logic gates based line follower). Spell out the exact problem statement you want to do.

Step2. List down all the different aspects/ modules you will have to cover (here: sensors, motor driving, power supply, logic gates design).

Step3. Use the internet to find out more about each. Look for general descriptions and approaches. Make yourself familiar with different terms, common ICs/equipments used.

Step4. THINK over the solution, YOUR solution. Think again. Try it out. Read datasheets/spec sheets before actually trying it out. Make a good, clean design on paper or computer before you actually try it out. Read the datasheet once again, now with respect to where you could go wrong (are you trying to draw 1.5amps from the 7812? )

Step5. If you fail, try finding out the reason yourself. Look where you have gone wrong. Go through the datasheets/spec sheets again.

Step6. If that doesn't work out, search for specific problems that you should have identified in step5. (Search this forum too )

Step7. If all fails (it shouldn't in 90% of the cases), post on the forum. This time, read the forum posting rules and guidelines first, specify the exact problem, give a complete description of what you have done (however embarrassing it is, which usually it is! :P ) and then you can expect elaborate help.

Step8. Try out the suggestions. In most of the cases, it should help you solve your problem. Rejoice!

Step9. Come back to the forum. Post (Brag) about your success, specify what was the problem and how it was sorted out, (thank those who helped ) and complete the topic! In doing so, you will help a lot of budding roboteers stuck at Step6!!!