It depends whether you mean "good" as in "easy to learn and practical to use" or as in "believable as being the naturally evolved writing system of a fictional culture created by the author". The two meanings of a "good" writing system would give very different results. Most real life naturally evolved writing systems have irregularities, ambiguities, borrowings, complications and accretions of alleged shortcuts that were quite obviously cobbled together by some random scribe in a hurry and then just "stuck". Usually the longer the culture has used writing the worse these are.
The creation of a "good" writing system in the first, practical sense would be the work of years for scholars and scientifically trained experts. Among the systems in daily use by large numbers of people, the Korean Hangul alphabet is regarded as one of the most logical. An aspect of Hangul you could copy is that the shapes of the consonants iconically represent the shapes the human mouth makes when forming them. Then again, there are advantages to a purely arbitrary set of phonetic symbols such as the Latin letters I am using now: you do not have to fuss about getting the representation right, just ensure the symbols are distinct and quick to write. The symbol set should not be too large to learn easily. The full form of the International Phonetic Alphabet is incredibly useful to people who study languages in depth but would be too unwieldy for daily use.
An efficient writing system need not be phonetic at all. Systems of ideographic symbols have been created with the intention that they could be used as an auxiliary written language for people of different spoken languages, for example Blissymbols.
Turning to making a good writing system in the second sense, that is, one that is a believable outgrowth of a fictional culture, your starting point would be the physical form of the beings, human or otherwise who used that form of writing, including what abilities, tools and materials they had to make permanent records. As ohwilleke's answer said, these could vary to an almost unimaginable degree.
Assuming human or human-like writers and an Earth-like world, your next step is to think about what materials they have to write with and on. For instance, runes that were originally cut into wood with a knife tend to be angular sets of straight lines. In contrast forms of writing that were originally written on leaves tend to be based on circular shapes because cutting straight lines along the vein of the leaf would split it. The cuneiform writing of ancient Sumeria used a wedge shaped tool to press marks into soft clay. If your system's first scribes have paper, whether they use brushes or quills will make a difference.
Historically logographic writing systems preceded alphabets, syllabaries and similar sound-based systems. But they didn't stay purely logographic, if they ever were. Quoting Wikipedia, "All logographic scripts ever used for natural languages rely on the rebus principle to extend a relatively limited set of logograms: A subset of characters is used for their phonetic values, either consonantal or syllabic." So if you intend to portray the writing of a society that has long been literate and has kept its traditional form of writing, a logographic system with an overlay of phonetic elements would be most plausible. Logographic systems tend to take longer to learn so writing is likely to be the preserve of an elite.
Societies that are more recently literate, or where there has been a reform of the writing system, would probably use a phonographic system. The website "Omniglot" has a list of types here. Languages with a restricted set of syllables such as Japanese are likely to use a syllabary, languages such as Hebrew or Arabic where most of the meaning is carried in the consonants are likely to use an abjad, and so on. Because phonographic systems are usually easier to learn, a higher proportion of the people are likely to be literate where one is used.
Finally, when people are conquered or influenced by another religion or culture, this also is likely to affect their writing system. It is very difficult to force people to change their spoken language but replacing the writing system is much easier, especially if few people can read.
