The way that I use is a capillary tube melting point test. It is certainly not the most accurate, but it will give you a good understanding of ID of a powder and even its purity if you are interested. Its cheap and easy but tt can make your BP read a little high due to the smallness of the sample, but not by much for our purposes.
Get a decent thermometer, one that has a fairly good range on it (mine goes to 360 degrees celcius if I remember correctly). You can find all kinds of them on ebay for about $10.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7556904819&ssPageName=MERC_VI_RSCC_Pr4_PcY_BIN_Stores_IT
Next get some one ended capillary tubes at a science supply store for about $5 or $6.
http://wardsci.com/product.asp_Q_pn_E_175020_A_Melting+Point+Capillary+Tubes
Hold the open ended side of the capillary tube down and tap it into a small pile of your powder. After 10 or 20 taps you should have about 1 to 1.5cm of powder in your tube and this will suffice. Turn the tube over and tap in on the table until the powder falls down into the closed end of the tube.
I usually just take a small rubber band and wrap around the capillary tube and bulb of the thermometer so that the end of the capillary tube (the end with your powder of course) is flush with the end of the thermometer bulb.
Next just heat water in a pan (large enough to see the powder in the capillary tube very clearly and can keep an eye on it the entire time). If you have any type of vision ware I believe it is called (the clear pots and pans) they work great, but I don't and regular pans work you just need to make sure you have a large enough pan to see down into easily.
For lower BP (<100 C) water will work, for medium BP (100 to <X<200) olive oil work as will grapeseed oil. For high BP (>200 C) Olive Oil will work just becareful not to exceed 200C and for high BP (>200 C) Silicon Oil is a good choice.
Since you have bases you are concerned with you need the higher BP liquid bath (silicon oil). It is very safe, very stable at high temps and has a low flammability. But as always you should exercise caution with these types of experiments.
When working with Olive oil or grapseed oil don't exceed 200 C, the smokepoint is about 210 for Olive Oil and about 240 for Grapeseed and can start to get dangerous and close to the flash point (approx 300 C)(yes, it will spontaneously catch on fire)
Now just starting heating your bath slowly, so the thermometer can keep up with the rising temperature. Just keep a close eye on your sample, especially close to your expected MP, and watch for when the first crystals start to melt record your temp, them also record the temp when all of the sample has melted. These should be within a few degrees of one another.
Compare these to the chart with expected MP's and you know what you have. A lower than expected MP, means a less than pure sample. The further below expected, the less pure.
Here is what you should compare to:
http://anabolicminds.com/forum/conversions/33545-steroid-melting-points.html?highlight=melting+point
I think I covered everything. If i missed something, let me know.