With nearly all technological advancements involve wireless links in their backbones, the efficiency of classical fixed RF systems is in question. This is further exacerbated with the crowding of the spectrum due to recent trends such as 5G and IoT systems, pushing wireless links to carry more data than their wired counterparts do. Adaptive wireless devices are a promising solution since they have the ability to adjust their response based on the circumstances. This enables optimizing the spectral usage and the efficiency of the overall wireless transceiver. This tutorial targets fundamental understanding of theory and implementation of adaptive and tunable wireless circuits and systems. Various tuning technologies will be introduced along with their circuits and trade-offs. This includes solid-state varactors, MEMS, ferroelectric and ferromagnetic devices. Tunable-adaptive circuits for RF filters, Power Amplifiers (PAs), and Low- Noise Amplifiers (LNAs) are also discussed in comprehensive detail, including tuning range, linearity, and power concerns. A few examples showing system-level implementation of such tunable circuits are also presented. CAD simulation examples are utilized to give the participants first-hand experience in wireless adaptive circuits and systems design.