I've read in some places that link trading is a good way to get in-bound links, but read in other places that link trading is punished by search engines.
Should I use link trading or is it counter-productive?
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If the links are from bad sites, then this will bring your site down. For small businesses particularly, cross linking is definitely a good technique, as you are likely to want to genuinely endorse each other.
Bought links are bad – don't pay a site to link to you, and if the site has millions of links, it won't count for much.
The sites that link to you can provide context about the subject matter of your site, and can indicate its quality and popularity. However, some webmasters engage in link exchange schemes and build partner pages exclusively for the sake of cross-linking, disregarding the quality of the links, the sources, and the long-term impact it will have on their sites. This is in violation of Google's Webmaster Guidelines and can negatively impact your site's ranking in search results.
To see why this practice has, at best, a net zero effect for both linking sites (assuming that the normalized number of outbound links are equal between the sites) and, at worst, a net negative effect for one - or both - of the sites (assuming that the normalized number of outbound links on Site A is far greater than that of Site B, such that the value of Site B's link to Site A is greater than that of Site A's link to Site B; both sites may be adversely impacted if reciprocal linking adds to the damping factor on each site's ranking) take a look at Wikipedia's PageRank entry.
The simplified algorithm presented at Wikipedia does not factor in any damping or additional factors considered by Google when determining the page's rank - it's still relevant in this case, however, as it illustrates the reasoning behind Google's discouragement of reciprocal linking schemes.
Generally (indiscriminate) link trading is frowned upon by SEs and often you will gain little benefit and may probably even face a penalty.
However, inbound links from worthy sites; sites in good standing, and ideally sites with complementary content can help a lot. I've no idea what are of business you are in, but contacting specific sites offering complimentary products and services and arranging a reciprocal link exchange might be useful, but simply registering with generic link farm will not.
There are plenty of others ways of getting inbound links - writing articles about your area of business and submitting them to news/trade magazine-type sites, or offering a free resource (information/service/download) are classic approaches.
But ultimately, you will only get decent inbound links if you have good/interesting/sought-after content, products or services - and you can't short-cut the issue through link farms.