Seminyak is small enough that most things are reachable on foot, but the heat and traffic make taxis sensible for anything beyond about ten minutes' walk. Bluebird taxis are reliable and metered — accept no substitutes; insist on the meter. Grab and Gojek ride-hailing apps work well in Seminyak (though parts of Kuta have prohibitions on app pickups; ignore the local touts trying to convince you otherwise).
Scooters can be rented from any of the dozens of small shops along Jalan Raya Seminyak for around 70,000–100,000 rupiah a day. International licence required; helmets compulsory; traffic is unforgiving for the inexperienced.