As a basis for learning about realism use photographs (at least to start with).Any photograph is of something.So instead of selecting random subject matter select the kind you'd like to paint.An artist who lived in California wanted to learn how to paint polar bears.In addition his painting skills were quite modest.I suggested he should do many small experimental studies by looking at photographs.It did not matter whether they were finished or not for they were ways of learning about bears.After 250 such studies he did his first painting with no polar bear or photograph.He was totally surprised at how well his polar bear turned out.In addition the standard of the work was infinitely better than it had been in the past.He had internalized his learning.The polar bears he created were his not any photographer's either for they were his!So if you want to learn to paint animals, then choose animal photographs.Like the Californian artist don't just select any animal focus on one (tiger, cat, horse).You get to understand your animal and over time you develop the individual paining skills needed.You will also know how to paint your subject your way and eventually you can focus on another subject.If it is related to your original theme you will learn much quicker.From one breed of dog to another is an example and then from one kind of animal to another.You'll note the similarities and also the differences.Follow this pattern for long enough, and you'll be able to paint anything!Painting a large number of experiments will develop painting skills, and also attitude.You'll become more discerning, because you acquire more experience.You'll not need, nor want, other people's assessments.Let's say you want to learn to paint dogs, then paint dogs not figures.BUT do NOT worry about how they turn out, just paint them and in time they'll improve.Maybe you don't believe this?Years ago I trialed an art education program in a primary (elementary) school.The art teaching process was very closely linked to the materials issued to the pupils.The particular material combinations chosen were not random.They were designed to introduce some quite specific experiences to the pupils.However their challenge was to see what they could create with any given combination.One teacher noticed a particular boy over a series of lessons.In the earliest lessons there were always two blobs present in the work.It didn't matter what he was given by the teacher.Over a period of time these blobs gradually changed into two birds.They were just basic symbol-type birds, such as most people might do.But as the lessons continued the birds improved.There were more details and eventually they became recognizable as budgerigars.The teacher realized this boy was making budgerigars no matter what materials he was given.He tried to find a combination of materials that couldn't be turned into budgerigars.The boy always found a way to make the birds.One time he even pin-pricked budgerigars onto paper.What chance was there that this kid might become the best budgerigar artist in the world?If he continued, I'd say every chance.Why did he do this?Well the teacher discovered (surprise) he had two pet budgerigars.They meant more to this boy than anything else.Because the teacher DIDN'T tell him what to do he could express his feelings and knowledge.He also got much better at it!That's how it should be learning to paint anything you want.Just do them.They'll improve provided the motivation is strong enough.