Transition metal doped ZnO has been studied from the perspective of its suitability in electronic applications. Bulk samples of Mn doped ZnO has been synthesized by solid state reaction and sol-gel techniques. Thin films of Mn doped ZnO has been synthesized by only sol-gel spin coating technique. So far as Co doped ZnO is concerned it is basically Co co-doped AZO [Al doped ZnO] film synthesized by sol-gel dip coating technique. Above 3 at% of Mn doping impurity phase has been developed for bulk powder sample. The impurity phase was completely or partially dissolved by ion beam irradiation. The role of Zn vacancy and substitutional replacement of Mn at Zn site is crucial for intrinsic ferromagnetism. Further counterbalancing antiferromagnetism and paramagnetism are also present. 2 at% Mn doped ZnO powder sample indicate metal insulator transition. Mn doped ZnO films exhibit defect induced ferromagnetism and interpreted in terms of bound magnetic polaron. Zn Vacancy favours and oxygen vacancy opposes intrinsic ferromagnetism in Mn doped ZnO film. Highly conducting Co co-doped AZO films shows potential for applications with interesting low temperature resistivity behaviour.