What are the best practices for data cleansing in Salesforce?

Data cleansing should be regular
70% of CRM data becomes obsolete each year, so regular data cleansing should become your routine. The most evident way to maintain data timeliness is to ensure that your in-house administrator or Salesforce support vendor regularly provides data cleansing with dedicated tools. Another measure you can take to fight obsolete data is to enforce weekly data cleansing activities to employees. For example, sales reps may clean up expired opportunity close dates and other CRM data, which is no longer relevant.
Data cleansing should be complemented with measures on sales-related processes improvement
Keeping your sales data clean is not a merely technical activity. It requires reviewing lead and opportunity management processes to unify standards for data input for different systems used in a company. For instance, sales reps use Salesforce Sales Cloud integrated with a marketing automation platform. If sales reps and marketing specialists do not have unified standards for data input (unified lead and opportunity name format, phone number format, etc.), duplicated data in CRM will be a result.
Data cleansing should be supported with proactive technical measures
According to 1-10-100 Rule, it takes $1 to verify a CRM record when it is initially inputted, $10 to clean it later, and $100 to do nothing (a result of lost opportunities and wasted time). To prevent the revenue drain caused by discordant sales data, you should take proactive technical measures to maintain data quality. For instance, an in-house Salesforce administrator (or the one from a Salesforce support service provider) can enable automated deduplication with Salesforce duplicate rules that help to identify and manage (delete, merge, etc.) duplicate records. The administrator can also introduce validation rules. They prevent the entry of data not compliant with the internal quality standards of the sales data in your company. For instance, a rule can validate that the opportunity’s close date isn’t prior to the current day or that the opportunity amount is a positive number.

Let’s take a look at some must-follow best practices for Salesforce data cleansing and mitigating the impact of bad data in any database.
There are a few best practices I'm listing down that any company must follow:
01. Verifying and updating your Salesforce contact data

02. Standardizing your Salesforce data for better analytics

03. Fix incorrect and/or missing Salesforce data?
04. Deduce your Salesforce data efficiently

05. Now You are Ready to start with Salesforce deduplication?

You can go through this blog to get in-depth knowledge about the topic
https://dataladder.com/salesforce-data-cleansing/?utm_source=forcetalks&utm_medium=content-promotion&utm_term=&utm_content=post&utm_campaign=traffic-gain

Here are the some best practices for data cleansing.

• Regular Data Health Audits
• Validation
• Use the Right Tools
• Internal Education