ATMs accepting Visa and MasterCard are ubiquitous.
Bosnia's convertible mark (KM or BAM) is pronounced kai-em or maraka and divided into 100 fenig. It's tied to the euro at approximately €1=1.96KM. Though no longer officially sanctioned, many businesses still unblinkingly accept euros, for minor purchases using a slightly cutomer-favourable 1:2 rate. Exchanging euros is markedly better than changing other currencies as there's no rate-split.
Exchanging travellers cheques usually requires the original purchase receipt.