Sketching is an exciting hobby to learn. That being said, if you are not too good at drawing, it might not be so enjoyable in the beginning. But... fear not! Anything and everything can be learned with a bit of dedication and hard work. You may come across several art courses, that can teach you the basics. But most such courses would burn a hole in your pocket and may not be congenial to your style of sketching. But, if you are willing to do the groundwork, anything can be self taught.
Mentioned below are some practical steps that you can adopt to learn how to sketch
First and foremost, learn all the basics. Taking into consideration the vast amount of literature that is available online, you shall be able to find several ebooks that can give you an insight into the basics of drawing, which can include the various mediums of art as well as the basic principles of the same.
You could also check out the innumerable videos available on online video platforms such as YouTube so as to witness how artists across the world create art through multiple mediums. Also, study anatomy if you wish to draw people. There are multiple books available online for the same.
Once you have had a good understanding of the basic principles of sketching, it's time to apply the same in your attempts at sketching. A good start would be trying to draw anything and everything that you see. The most important aspect to be kept in mind while doing it is that it's okay to make mistakes. Everyone makes mistakes, even the best of the artists. It could be the difficulty to achieve the right proportion for the different parts of a human body. Or it could be the difficulty to capture the subject of your drawing within the boundaries of the canvas.
It could be anything! But after a few attempts, you will learn how to rectify your errors to slowly achieve perfection. Carry with you a sketchbook at all times. Draw whatever you see. This practice would also assist in ensuring the expansion of the scope of subject matter that you can draw. There are certain artists that can only draw a certain set of images. I am not implying that it's a bad characteristic, but it is always good to achieve fluidity with respect to the subject matter that you are capable of drawing.
Once you have learnt the basics of sketching and you have made several successful attempts, try to focus on achieving perfection. Try your hand at shading and learning about lines, tone and texture. Suppose, you are drawing a human face. Try to bring in shades to the different features depending on the contours of the face as well as the placement of shadows. I must admit that this is a slightly tough task and would require a lot of practice.
You could start with simple figures such as a cube or a sphere wherein you could try to capture the shadows through shading. Once again, keep at it, because it's worth it! Your sketches would look much lifelike and wonderful once you have achieved a certain level of mastery over shading.
Once you have achieved all of the above, it's time to level up the game. Start working on different mediums, different brushes, different pencils! Learn how to use the different art equipments to capture whatever you want. Learn the advantages and limitations of each tool and use the same accordingly to achieve the desired results.
The aforementioned description summarizes the various steps to be adopted to learn sketching. In addition, surround yourselves with artists. There are several art communities such as Deviant Art and Behance, with a huge number of artists registered. Interact with them, learn about the different styles they have adopted in creating art. Not everything can be learned from a book.
And finally, struggle! Keep working hard! Constantly practice your sketching. It might not come easy. Your drawings may not be good in the beginning. But with continuous practice, persistence and determination, you shall see the scribbles and doodles that you started with evolve into beautiful works of art.