Boeing 247 the ils interception point is always at 10nm which you will find marked on an ILS approach plate on the vertical profile for the approach shown on the bottom of the chart. Generally it is at 3000 ft AGL however there are some ILS approaches that are steeper at 4 degrees but they are catered for by giving you a glide path signal further out but these are rare. There are a lot of ILS where you intercept the glide path at 7 nm or abut 2100 -2500 feet and some further out at 13 or even 20nm at a higher altitude, generally the reasons for these approaches is do with the siting of the ILS equipment on the ground at the airport. You will note from looking at a lot of the charts that for most ILS's there is a NDB or locater beacon at the beginning of the ILS which you have to tune up using your ADF and this will give you a positive fix when you pass it if you do not have DME or it is not a co-located with the ILS and not all are. They are also very useful to track to a point to pick up the ILS but generally have a very short range of only about 20 nm.

AT 10 nm if your on the localiser the vertical beam of an ILS the vertical ILS needle and the glide path needle will be centred as well. In my flying you should be at final approach speed at this point and this point was time for gear down and minimal flap changes until past the check height shown by the maltese cross on the approach plate, flying the profile and being configured means you can make minimal attitude changes and power changes and basically slide on down the ILS to minimums.

You will note that you can pick up the localiser beam well before the glide path beam and the ILS needle will be indicating fly up or be above the centre until you hit the 10 nm point when the both centre and then you merely follow the commands indicated, needle going up means fly up, needle going down fly down, needle left go left, needle right go right. Be aware however that this all changes once you start to go past the end of the runway and fly away such as in a go around when the needle sense becomes reversed so if it indicates to the left you go right etc.

Hope this helps.