First of all by experience.
As we have been working in this business for many years (over 15 years), professional relationships have been established with partners in different countries around the globe. This allowed us to know the quality of the service to destination and to be sure of the professionalism of these companies and vice versa, it allows us to receive imports from these privileged partners.
Then by the international networks.
Many companies belong to networks of removals (IAM, FIDi for the most known) or seriousness and skills are an obligation. We also ask our privileged partners if they know competent companies in the country in question whether it is a neighboring country.
And finally the Embassies.
Being in a French speaking country, we ask the French Embassy in the country of arrival which removal companies are recommended by the Embassy or conversely are to be avoided.
Anyway, we prefer to refuse a move than to send it to a company of which we are not sure of the skills.