INTRODUCTION
Consonant clusters (group of two or more consonants) appear frequently throughout the text, with some appearing more often than others. In order to increase speed of writing and condensing the text, special ligatures were created. These ligatures (characters that represent a compound of two or more consonants) are very useful and are used frequently. For example, the cluster ‘tr’ has a special compound character, as you can see below:
त् (t) + र् (r) + अ (a) = त्र (tra)
The character ‘त्र’ (tra) is a called a special ligature, since only a handful of them have a special form. We shall now be exploring the most common ones you can find in literature.
DUE PROCESS
While all of the special ligatures are a single uninterrupted character, most of them are created with a straight-forward logic. The preceding consonant is usually given the top or the front space of the ligature while the succeeding consonant is given the bottom or the back space of the ligature. Observe how the following special ligature is created (colour-coded to highlight the backbone):

Some are not so obvious but it doesn’t matter because there are relatively few of them. In the section below, you can see a chart of these special ligatures.
SPECIAL LIGATURES CHART

Remember that you may wish to omit the special ligature altogether to favour the more systematic way. However, both versions are correct and readable.

SYNOGLYPHS
Due to changing times, some characters have been modified. Yet, the older forms are very much used while writing, though it may be obsolete in some parts. As such, there are two glyphs that look different but have the same meaning and pronunciation. These glyphs are also known as synoglyphs.
While writing with hand, the synoglyph is more likely to be used.

Also, some people choose to omit the loop around certain characters like ग (ga), भ (bha). This results in a much more sharper look (on the picture below, the right one):

In the end, which version you choose is a matter of preference. I personally omit the loops but many people I know do not. As long as it is legible, it shouldn’t pose any problem.
EXERCISE
IDENTIFY THE FOLLOWING SPECIAL LIGATURES
1. न्न
2. त्र
3. द्य
4. ङ्ग
5. त्त
6. द्ध
7. श्र
ANSWERS
1. nn(a)
2. tr(a)
3. dy(a)
4. ṅg(a)
5. tt(a)
6. ddh(a)
7. śr(a)