People who are not family members will not benefit from your estate unless they are specifically named as beneficiaries in your Will.
Sometimes, a Will provides for personal possessions to be distributed by Trustees, without specifying individual beneficiaries. A letter of wishes can be used to indicate if you have any particular friends in mind for particular possessions. This would enable you to explain the reasoning behind the gift. However, although Trustees usually carry out your intentions as they appear in a letter of wishes, the letter is not legally binding on them.
In theory it would be possible for you to leave your whole estate to friends even if you have close family or dependants. But a claim could be made against your estate by a family member or dependant for reasonable financial provision to be made for them.
If a friend owes you money at the time of your death, your Will could include provision for releasing the friend from all or part of the debt.