As in most tasks, simple common sense will get you a good way. In terms of tools you will need nothing more than a pack of filing cards to record details of each person and a considerable amount of free time to spend in front of microfilm readers and, on your exceptionally favoured days, actually handling the real records, though this is a luxury most libraries, in the cause of preservation, can no longer grant.
You can also buy, or acquire via shareware, several programs to help organise your family records - the commercial offerings will also include a 'How to get started' manual - your local bookshop or public library will also have a good selection of introductory books. Your local genealogy society (address from your local library) will also be a good source of advice.
Start by writing down all you know of your family - names (both personal + family), relations (parents, offspring, siblings etc.), dates (approximate if necessary), places (of marriage, death/burial etc.) and any family 'legends' (most of which will be just that, but will often contain a grain of truth that will enliven someone's history). Older members of the family will help here - women generally have a better recollection of personalities than men so use this an an excuse to visit those long ignored great aunts! Don't forget to record words on tombstones etc. and obituary notices in local papers, though as these are seldom indexed you will need to have approximate dates before starting your search.
The best place to start is the death certificates of say your grandparents or great-grandparents - the address to which to write, cost etc. obviously depend on the jurisdiction in which the death was recorded (local libraries will generally help here). This should give you date of birth and parents (though as you will find in many other cases there is no guarantee that the information is 100% accurate) - from this information birth certificates can be ordered. You will also need marriage certificates - these will generally give both sets of parents and their occupations. Now repeat the process for each preceding generation until you get beyond the date at which civil records were kept. Even in in this simple task you are likely to have 'gaps'. Depending on the jurisdiction you may find that the information available from such civil records is also available, more cheaply, via Mormon microfilms.
Once you get back pre 1900 then census returns (available from Mormon microfilms) will often provide further valuable information as to residence as well as a guide to family structure - generally more complex than today's simple nuclear family.
Once you can determine the name, approximate birth date etc., of your Manx ancestor then the material on the rest of these pages will, I hope, give you some guide as to taking your ancestry back.