If you are looking for the ei only then a series of exposures that range from 3 stops under the meter reading to 6 stops under the meter reading in half stops should be adequate. Leave one or two frames (with roll film and 35 mm) blank. If you are testing sheet film, toss in an unexposed sheet. Process as normal. Now after the film is dry, use the densitometer to determine film base + fog by measuring the clear frames or clear sheets. Write that number down. Now measure each frame and find the frame that will be the nearest the .10 density. This number will be the ei of that film. Don't forget to subtract the film base + fog and then find the .10 density. keep good notes so you will know what frame is what.
To find the development time, we are interested in the frame about 3 stops over the meter reading. Run the test and start 2 stops over to say, 4 and one half over. Process the film at the manufactures published time. Using the densitometer, find the density that is closest to 1.20 for condeser enlargers and 1.30 for diffusion enlargers. If you are way under processed or way over processed, then another test is needed. Way over is generally the problem. Start to process the film and reduce the process time by about 20%. Read the film and adjust as necessary. Pretty simple if time consuming.
A quick suggestion to RAP's reply - It should be noted that the photographers he mentions (Barnbaum, Sexton, Adams) all shot or shoot large format. If ytou are shooting smaller format you might find that these ratings are not in line with what you desire. Its always best to take the film for a "test drive" meaning - shot, develop and print on the grade you like and at the size you wish to print. If it is not correct, then make your adjustments accordingly.
As a reply to mvjim.
I agree that sheet film and roll film considerations are not the same.
Typically the published desired densities for sheet film reflect the desired grade two paper grade.
Roll film will benefit from a development that will allow printing on a grade three paper. The reason that I say this is that roll film will benefit from lower development times that will reduce the formation of visible grain.
This will still allow the availability of grades four and possibly five (depending on the paper chosen) for expansion of contrast. It will allow grades two and one in the event that contraction of contrast is desired.
I don't think that if all things are equal (the same film emulsion and accuracy of lens shutter speeds) that roll film will benefit from a different EI then that determined for sheet film. The film emulsion is governed by laws of sensitometry and thus it requires a given quantity of light to expose a given film emulsion. The emulsion characteristics give no weight to differing film formats.