As every file is different (advisory/litigation, specific question or recurrent intervention), your lawyer will provide you with a fee estimate and the applicable terms and conditions before providing any service. The aim is to be completely transparent.
Fees can be calculated on a time-spent basis, with an hourly rate, or on a fixed fee basis. The fee agreement may also provide for fees depending on the major steps of the file.
In specific matters, a flat rate fee can be combined with a performance fee, i.e. an additional fee based on success or on the result (e.g. savings).