A. This will depend on the terms of the lease and the circumstances that you are in.
Some leases contain provisions that either party can terminate the agreement unilaterally (individually) by giving notice to the other. If this is the case in your lease, then it will be a case of giving valid notice to your landlord. It is rare that these clauses are included in commercial leases as it removes the certainty that both parties will ultimately desire.
There may have been a break clause negotiated into the lease. This occurs when there is a provision that the tenant has an option to terminate the lease after the 3rd year of a 7-year term. It may be worth consulting the lease to see whether there is a break date coming up soon. If there is, work out whether it makes commercial sense to wait until that date or try and get out of the agreement earlier.
Depending on any prohibitions (limitations) contained in the lease, a tenant may also be able to assign (transfer) or sub-let their interest. Commercial landlords will often draft leases to allow the option for a tenant to assign or sub-let because it is commercially sensible – it allows the tenant a degree of flexibility. In these situations, it is likely that the landlord will want to include provisions to give them an element of control over who a tenant may want to assign or sub-let their lease (e.g. the outgoing tenant may be required to act as a guarantor for the incoming tenant, or the tenant may only be able to assign or sub-lease to an entity who has demonstrated that they will be able to keep up with the rent payments).
As a final option, it may be possible to negotiate with a landlord to surrender the lease. However, this will usually be against the landlord’s best interest, and they will expect a significant payment to agree with this.