Any time is a good time for tax planning, but the best time is as early as possible, preferably before coming to Portugal and before having a NIF issued.

People who are coming to Portugal with a certain business structure will very rarely be doubted, even if the structure is highly efficient from a tax perspective. People who change structures will often be questioned by the tax authorities. Changing structures after coming to Portugal is not impossible, but it's much harder than doing it early.

More on this here.
The Non-Habitual Residency tax regime is a 10-year preferential tax regime in Portugal, targeted at people who have not lived in Portugal for the last 5 years. See our guide to NHR.
Anyone who has not been a tax resident in Portugal for the last 5 years can use the NHR as long as they apply on time (up to 31 March the year after becoming tax residents).

People often confuse eligibility and use of the NHR system and more specifically, one of the benefits of NHR is a reduced tax rate in certain high value professions. However, having one of these professions is not a requirement in obtaining NHR status and we often advise people how to benefit from the NHR even if they are not working in any of these professions.
It depends on the type of advice that you want.

Tax lawyers are experts in tax planning. A tax lawyer looks at the sources of income and will suggest ways to utilise tax breaks and reduce the overall tax burden. The advice given by tax lawyers is confidential and remains between their clients and themselves. As experts of the law, tax lawyers are usually more expensive than accountants and charge for consultation.

Accountants are experts of auditing and doing the books. Their primary role is to help their clients with reporting requirements. Many accountants will offer tax advice to their clients . If a tax case is audited, tax accountants have to disclose the advice that they gave to their clients.

Ideally, you should use a tax lawyer for tax planning and an accountant for ongoing administration and bookkeeping.
Would you prefer to be operated by a surgeon or by a family GP?

Many firms in Portugal offer a wide range of services, ranging form immigration, to property, civil litigation and they also offer tax advice.

Indeed, we would expect any lawyer to know "a little bit about everything" but believe us - tax law is really complicated and it is also very creative. So yes, it is easier to use the same people you already know for everything you need, but it is unlikely that they will have the expertise and depth of tax knowledge to give the best advice.

Apart from being tax lawyers who focus our practice on advising expats, we are also an international boutique with qualified lawyers from Portugal and multiple other jurisdictions.  

The reason that this is so important is that the NHR system does not allow Portugal to impose tax in many cases when the other country has the right to impose tax. It is therefore impossible to advise on Portuguese taxation without understanding the systems that interact with it and who is better placed to understand such system than lawyers in these jurisdictions?

When we create a tax plan, we consider how the countries' different tax systems interact with each other, we understand the sources of income and the different forms of incorporation and investment vehicles used by people.

And finally, we offer big-4 quality advice and solutions in accessible prices.

We have qualified lawyers in the UK, US and Portugal but we advise expats who are coming to Portugal from all countries. We are experts of reading and understanding double taxation treaties and we have very good familiarity with exit taxes and similar situations.

We do not advise on taxation in countries where we are not qualified but we often coordinate advice with a tax expert in the country that people come from. Our advantage is knowing how to do that - what questions to ask, and how the systems interact with each other. 
Many people don't understand the difference between international tax lawyers and high street accountants. Think brain surgeons vs. a family doctors.

At FRESH, we do a lot as free service to the community. We encourage everybody to join our free FB group, read our free content , use our free taxbot or the free tax calculator.

However, our time and expertise is reserved to our good paying clients.
When a person moves from one country to another, more than one legal system is involved and often, more than one tax expert is needed.

At Fresh, we normally have a lead advisor whose responsibility is to collect all the facts. This advisor would be an expert in one jurisdiction. Such lead advisor will discuss the situation, as needed, with tax advisors qualified in all the involved jurisdictions.