Hi
Here are some of the things and processes that I currently use.
I would not recommend that a beginner start with modifying or mixing and matching, rather that they start with recipes, masalas and bases all from the same author. There are plenty of great ones on this site
Also, anything I suggest is just my own preferences and opinions at this time, not necessarily correct or what a real BIR would do, and most certainly subject to change.Always buy vegetables from a good green grocer, they are generally cheaper than the supermarkets and there always seems to be something funny about supermarket garlic if you ask me.
Garlic & Ginger paste - Always use fresh garlic and ginger (50/50) blended in your blender with a little sunflower oil. I make a big batch in an air tight container and keep it in the fridge. It will keep for a long time this way. Pre-made products are convenient and some such as Natco for example are pretty good - but they just don't produce as good result as making your own paste.
Tomato paste - I have had massive problems with tomato paste in the past. This has been mentioned before by myself here on the forum and noone paid much attention, but whether you believe it or not, the tomato paste even in small quantities has a profound impact on the taste of the final dish. Always use a brand like White Tower. Fill an average plastic TA carton 3/4 full and add at least 2tsp tandoori masala powder and 4tsp garlic powder, blend with Sunflower oil and a little water. Again will keep for a long time this way in an air tight container in fridge.
Use CA's Tandoori Masala -
http://www.curry-recipes.co.uk/curry/index.php?topic=1514.0 - My own opinion is that packet mixes are not as good as this mix by a long way.
Make up 2 litres of the "Spiced oil in base" that you can find from this thread -
http://www.curry-recipes.co.uk/curry/index.php?topic=5015.msg48518#msg48518Personally I do not use this in the base at all. I use this oil for cooking the main dishes. The above oil also produces the onion / pepper paste that can be blended smooth or be used as is in Dopiaza style dishes. It is absolutely superb and is a major factor in the process, dish aroma and taste.
Base (curry sauce) - At the moment I like to use CA's base -
http://www.curry-recipes.co.uk/curry/index.php?topic=3772.0I modify it a little by always making double (it does seem to add extra depth for some reason).
Always use Spanish onions only (some say the onions make no difference - a side by side comparison tells me I like Spanish onions better).
Use Bruce Edwards masala
http://www.curry-recipes.co.uk/curry/index.php?topic=1546.0 although, many of them are very similar, also has recent sucess with JB's masala too
http://www.curry-recipes.co.uk/curry/index.php?topic=4908.0.Add a couple of small potatoes and half the amount of fresh coriander.
I have currently settled on the above as it is very very close to the base sauce that I got from my local TA. Things I plan to try in the future is to add some form of stock (perhaps chicken) to the base as the TA's one appeared to have that extra meatiness.
Always blend the base to perfect smoothness. I personally find it more convenient to blend to decent smoothness then package up for the freezer, then use the stick blender to achieve perfect smoothness for individual portions just before cooking.
Heat, well flames do not seem to be necessary, they sometimes just happen as part of the process, it can be impressive to perform for the guests though. Cooking on a high output burner works for me, and cracks out a finished curry in a very short time just as a BIR would. This has been discussed elsewhere to death, so lets leave this one!
SPices - dull spices make for a dull curry. Avoid the supermarket spices like the plague, they are overpriced and always lack pungency. Find a good grocer with brands like East End, Natco, Rajah etc.
Next on my list of things to investigate will be something like 'green chilli pastes' as discussed by JerryM - there is something in that I think

I think we all need to remember, is that this BIR cooking business is just like building a fast car, there is not just one magic component that will help you win the race, it is the coming together of several parts, just because you have good engine is not enough, you then need uprated brakes, better suspension, a new exhaust system etc etc, take one part away or add one sub standard part and the whole product diminishes.
Well that should be enough waffle for now. Anyone else care to share some of their processes - although I am sure they have all been discussed elsewhere, sometimes reiteration can remind us all.