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When the optical pulses emitted by a laser become so short in time that they encompass only a few cycles of the carrier wave, the phase between carrier and envelope becomes a crucial parameter. The ability to control this carrier-envelope phase (CEP) is elemental to experiments probing the fastest processes in the microcosm, occurring on the time-scale of attoseconds. More than a decade into the attosecond era, the limitations of the established CEP stabilisation technique have begun to curtail experimental progress. First, increasingly complex experiments require many hours of uninterrupted operation at the same waveform. Second, the pulses used in experiments are approaching the single-cycle boundary, calling for ever-decreasing CEP noise. With the conventional stabilisation technique, already these two requirements cannot be fulfilled simultaneously. Ultimately, the low efficiency of the underlying nonlinear processes can only be compensated by driver lasers at a higher repetition rate than available at present. In order to advance attosecond pulse generation, novel approaches to CEP control thus face a threefold challenge that outlines this thesis: To simultaneously provide low CEP noise and long-term operation to present-day few-cycle lasers and amplifiers, and to investigate CEP control capability in high average power sources that are currently under development.\n\nThis thesis describes the adaptation of cavity-external CEP stabilisation for use with few-cycle pulses. The intrinsic limitations of the conventional feed-back technique are lifted. A laser oscillator is demonstrated to maintain record-low CEP noise for tens of hours of operation free from phase discontinuities. In addition, a modification of the technique is presented that further enhances the applicability to amplified systems. \n\nTwo routes are investigated to achieve CEP control in system architectures that represent potential megahertz repetition rate driver sources. In combination with temporal pulse compression, a thin-disk laser is shown to yield few-cycle pulses. Experiments are presented that provide the groundwork towards the first CEP-stabilised thin-disk oscillator. The second approach targets the seed oscillator of a fibre chirped-pulse amplifier. The CEP noise properties of different amplification regimes are examined. Intensity enhancement of the output pulses in a passive resonator is shown to benefit greatly even from a coarse lock of the CEP slip rate.\n\nFor few-cycle pulse energy to reach the millijoule level and above, amplification and temporal compression will remain indispensable in the foreseeable future. Maintaining CEP stability across such stages is crucial, irrespective of the technology employed. Cavity-external CEP control is demonstrated to enable more than 24 hours of constant-CEP operation in chirped-pulse amplifiers. Furthermore, a novel actuator is introduced that, in conjunction with a fast means of measuring the CEP, is able to provide phase correction of the amplified waveform up to several kilohertz bandwidth. The result is a train of millijoule-level pulses with residual CEP noise comparable to that of state-of-the-art nanojoule oscillators. Eventually, an experiment is presented to examine the influence of different types of hollow-core fibre-based temporal compression on the CEP. The findings shed new light on the origin of adverse effects introduced by this technique, and point out ways towards effective compensation.