Ensure you know the visa requirements of the country you are visiting well in advance. The best place to find this out is here.
Follow the guidance and fill in the forms carefully. Provide exactly the information required and in the correct format.
For certain countries your passport must be valid for 6 months after the date you travel. Check the entry requirements before you go, and remember to allow enough time to renew your passport if necessary.
Make sure you have all the required documents to hand. Some visas require a detailed travel itinerary, health information, invitation letters, proof of vaccinations, and a specific size and number of passport photos.
If organising a visa for a colleague, don’t assume they have a British passport, and check that the name on their passport is the same as the one they use for work. Visa requirements vary according to which country issued the passport, not the country in which the passport holder is resident.
If applying by post, photocopy all the relevant paperwork and send your documents by registered post. Allow plenty of time for getting a visa: sometimes applications are dealt with in the country you are visiting, so be aware that it may require your passport to be sent away for a period of time.
Depending on the country you are visiting, it can be useful to contact their UK-based embassy or High Commission for advice.
If you require a visa at short notice, you can visit the issuing office in person, although this normally involves an additional fee and a lot of queueing. Alternatively, you can use agencies that provide a visa service for a fee, which may be useful if you are not based in London. Check the agency is a reputable firm before employing their services.
Visas can be expensive to obtain so make sure they are budgeted for.