If you are a beginner, unfamiliar with the use of binocular microscopes and insect keys I would recommend joining the British Entomological & Natural History Society (BENHS) and attending a few of their workshops first. This will give you a feel for the kind of equipment and expertise you need – it will also bring you into contact with other entomologists who might be able to give you some good pointers as you start to take up the hobby. Then, once you are happy that you have the correct equipment and you still want to study Tachinidae, read on…
A simple binocular microscope (up to x40 magnification) with a good lighting unit is sufficient to let you see most keying features easily. It is worth shopping around but I got my microscope from Meiji Techno UK (formerly Hampshire Micro) and would certainly recommend them to anyone. It is a good idea to buy a high quality one – you can get a new microscope for around £250 but it may be better to save for longer and buy one in the £1000+ bracket with a good fiber-optic or fluorescent lighting unit. The improved clarity and resolution you get will make identifications a lot easier and will help reduce eye-strain. Good second-hand microscopes do sometimes come up for sale so keep a look out in the dealer’s catalogues. Whatever you do make sure you test plenty – take some specimens along and compare different styles and makes.
A list of books is given in the bibliography and these contain good identification keys to everything we have (or are likely to have) here in the UK. The keys are relatively straightforward and have clear diagrams – though there are always quirks to any key and some prior knowledge is helpful.
Sadly, anyone studying Tachinidae must be prepared to take specimens and maintain a voucher collection – most cannot be identified while alive. A reference collection is a vital tool to aid your own study but also allows others to follow on after you and either confirm your identifications or re-check your vouchers after a species is split into two or more species. This group is very complex and quite poorly studied at the moment so it is likely that changes to their taxonomy will occur in the future and without vouchers it might be impossible to use old records.
While on the subject, having a good voucher collection nearby can be very useful for comparing your specimens with those that have been identified by experts. The Natural History Museum (London) has the largest collection but it can be tricky to visit if you are working during the week or live a long way from London. The BENHS has a good (but incomplete) collection at its Dinton Pastures (Reading) office and Oxford University Museum has the second largest collection in the UK but the nomenclature used in some sections is old.