Your questions had two parts to it: (1) Encouragement. This isn't really dependent on anything as you can encourage anyone unconditionally, i.e. "You can do it! I believe in you!" (2) Praise. This can be looked at from different points of view. It sounds like you may have very high standards if you say they "never do anything to get praise". Even small things could be worth praise. A small child tying their shoe can be worthy of a "good job!"; it can depend on the age. Even small improvements from something that is currently "bad" can be worthy of praise: "Wow, you raised your D average to a C, you are really improving! Keep up the good work!!!" Also, kids can see negative attention being better than no attention at all. If you need you child to be quiet for 30 mins and they are quiet for the first 10 mins, do you praise them for being quiet after 10 mins (giving positive reinforcement so they will be quiet for the next 10 mins) or wait until 20 mins go by and they make noise and then yell at them? Which do you think would work better?

You have posted several (many?) questions about children. Specifically issues you are having with yours. At this point you need to seriously consider professional help. Your have a "problem child" on your hands and you need extraordinary solutions to these problems. solutions that are not easily pulled out of a hat, solutions that will require a therapist getting to know a lot more about the child, you and the home situation before any work toward resolving these issues can be done. I know that this can be an expensive proposition, there are therapists that work on sliding scale and most cities and counties have "public health" or "free clinics" which can get you into cheap programs that will help. Your family doctor can point you in the right direction. Failing that you can do a web search for your county/city mental health clinics. Or Public Health. Something like: (Your county) Public Health Should give you enough hits to locate your county's public health operations page which will most likely have an area of services. Going through them will require a lot of leg work, a lot of paper filing, however the outcome will be a cheap if not free good therapist. Seek a Therapists a psychologist not a Psychiatrist. Psychologists do not carry and MD, they can not prescribe drugs. As such they must deal with the issues via talking. Psychiatrists do carry an MD, although trained in psychology they tend to spend 15 minutes with a patient and prescribe too many drugs too early which in many cases makes the problems far, far worse or can really screw up the child. I'm not saying that drug therapies may not be needed, I am saying that you need a professional to talk with the child to exhaust non-drug routes before applying drugs to the problem. If your child has entered the Teen years then most likely it is puberty going down hard for the child. Having a therapist work with the child to deal with all of the issues of those years may be the best route. Short circuiting the puberty era via drugs could most likely lead to your child growing up half an adult, not fully able to function as an adult for life. IF drug therapy is needed, you need to back that up with talk therapy for the best results.